More than 40 publications about the CTR-Test® have been released since 1990. You will find a selection of the most significant publications on clinical studies and on the application of the CTR-Test® to analyze patient specimens (validation studies). In total, 18 clinical studies with about 2,400 examined patients have been published. These studies prove the predictive power of the test and the benefit for the patient. On top of that, 11 validation studies with about 21,000 patients have been conducted to verify the test on patients specimens.

Here you will find a list of the articles and abstracts, which are mentioned on this site:

A comprehensive clinical evaluation as part of the quality management can be found here:

Clinical Studies

1. Highly specific prediction of antineoplastic drug resistance with an in vitro assay using suprapharmacologic drug exposure

J Natl Cancer Inst. 1990 Apr 4;82(7):582-8.

Kern DH, Weisenthal LM.

Bayes' theorem has been used to describe the relationship between the accuracy of a predictive test (posttest probability) and the overall incidence of what is being tested (pretest probability). Bayes' theorem indicates that laboratory assays will be accurate in the prediction of clinical drug resistance in tumors with high overall response rates (e.g., previously untreated breast cancer) only when the assays are extremely (greater than 98%) specific for drug resistance. We developed a highly specific drug-resistance assay in which human tumor colonies were cultured in soft agar and drugs were tested at high concentrations for long exposure times. Coefficients for concentration x time exceeded those reported in contemporaneous studies by about 100-fold. We reviewed 450 correlations between assay results and clinical response over an 8-year period. Results were analyzed by subsets, including different tumor histologies, single agents, and drug combinations. Extreme drug resistance (an assay result greater than or equal to SD below the median) was identified with greater than 99% specificity. Only one of 127 patients with tumors showing extreme drug resistance responded to chemotherapy. This negligible posttest probability of response was independent of pretest (expected) probability of response. Once this population of patients with tumors showing extreme drug resistance had been identified, posttest response probabilities for the remaining cohorts of patients varied according to both assay results and pretest response probabilities, precisely according to predictions based on Bayes' theorem. This finding allowed the construction of a nomogram for determining assay-predicted probability of response.

2. Cost-effective treatment of women with advanced ovarian cancer by cytoreductive surgery and chemotherapy directed by an in vitro assay for drug resistance.

Cancer J Sci Am. 1999 May-Jun;5(3):174-8.

Orr JW Jr, Orr P, Kern DH.

Purpose: Epithelial ovarian cancer is the fourth leading cause of cancer-related death in women. Five-year survival is about 25%, and new approaches to the treatment of this disease are dearly warranted. This study was designed to determine the feasibility of using an in vitro assay for drug resistance to guide treatment after cytoreductive surgery. We present preliminary results of this study after a median follow-up of 24 months.
Materials and Methods: We treated 66 patients with advanced ovarian cancer by use of a combination of cytoreductive surgery and chemotherapy. Patient inclusion criteria included histologic confirmation of epithelial ovarian cancer, International Federation of Gynecology and Obstectrics (FIGO) stage III, no prior chemotherapy or radiation therapy, no coexisting neoplasm, and optimal residual disease (< 2 cm). Malignant tissue from the involved ovary of each patient was tested in vitro for drug resistance, and chemotherapy was directed individually by assay results. On the basis of the assay we treated 19 patients with platinum/paclitaxel (TP) and 47 with platinum/cyclophosphamide (CP).
Results: Three-year survival (Kaplan-Meier estimate) was 69%; the 95% confidence interval was 58% to 80%. There was no difference in 3-year survival between the 19 patients treated with TP (66%) and the 47 patients treated with CP (74%). The cost-effectiveness of each treatment option was determined. It cost $4615 to achieve 3-year survival for patients receiving CP and $17,988 to obtain a similar survival with TP. The cost-effectiveness of assay-directed therapy was $9768.
Discussion: Because of the high recurrence rate and the poor long-term survival of women with advanced ovarian cancer, improved therapies for this disease are needed. After surgical debulking, we used results of an in vitro assay for drug resistance to individually select chemotherapy for the patients in this study. Although the 3-year survival of 69% obtained in the present study appears good compared with previously published studies of optimally debulked patients, the results must be viewed with caution. Patients were not randomized, and differences in prognostic factors, such as tumor grade, patient age, and performance status, could account in part for the higher survival found in the current study compared with previously published studies. Treatment with either CP or TP resulted in equivalent 3-year survival. The cost to achieve 3-year survival with this protocol, including the cost of the drug resistance assay, was $9768. We believe that consideration of costs avoided by the elimination of ineffective treatments, needless toxicity, and loss of quality of life would likely increase the cost-effectiveness of assay-directed therapy compared with conventional therapy. This study demonstrates that it is feasible to use an in vitro assay in routine clinical practice to eliminate ineffective chemotherapeutic agents.

3. Breast cancer survival and in vitro tumor response in the extreme drug resistance assay.

Breast Cancer Res Treat. 2001 Apr;66(3):225-37.

Mehta RS, Bornstein R, Yu IR, Parker RJ, McLaren CE, Nguyen KP, Li KT, Fruehauf JP.

Purpose: To determine whether in vitro extreme drug resistance (EDR) assay results for patients with breast carcinoma were associated with clinical outcome after chemotherapy.
Patients and Methods: EDR assays were performed on tumor tissue obtained from 103 newly diagnosed breast cancer cases. EDR scores of 2 for low, 1 for intermediate, or 0 for extreme drug resistance were determined for each agent tested. In vitro EDR scores for 4-hydroxycyclophosphamide (4HC) and doxorubicin were summed for patients treated with AC, or for 4HC and 5-FU for patients treated with CMF. Treatment selection was blinded to assay results.
Results: Median time to progression was significantly shorter for patients with extreme or intermediate in vitro resistance (n = 55, 48 months), compared to patients with low in vitro resistance, (n = 41, 100 months, p = 0.022). Patients demonstrating extreme to intermediate drug resistance also showed poorer survival than the low resistance group (49.5 months vs. not reached, median follow-up 48 months, p =0.011). Summed EDR scores, stage, and number of lymph nodes were significantly associated with survival in univariate and multivariate analysis. Compared to EDR scores of 4, summed EDR scores of 0-1 and summed EDR scores of 2-3 were associated with a relative risk of death of 3.09 (95%, CI 1.05-9.06, Cox proportional hazards model, p = 0.040) and 2.35 (95%, CI 1.07-5.15, Cox proportional hazards model, p = 0.033), respectively.
Conclusion: Extreme drug resistance testing identified patients with individual patterns of drug resistance prior to therapy. In this cohort of breast cancer patients treated with chemotherapy, summed EDR scores were significantly associated with time to tumor progression and overall survival. EDR results may offer a method for optimizing treatment selection.

4. Association between in vitro platinum resistance in the EDR assay and clinical outcomes for ovarian cancer patients.

Gynecol Oncol. 2002 Oct;87(1):8-16.

Holloway RW, Mehta RS, Finkler NJ, Li KT, McLaren CE, Parker RJ, Fruehauf JP.

Objective: The initial clinical response to platinum is a major determinant of outcome for patients with ovarian cancer. This retrospective study was undertaken to correlate the response and survival of newly diagnosed advanced ovarian cancer patients who received platinum-based therapy with in vitro drug response to cisplatin or carboplatin measured as percentage cell inhibition (PCI) in the in vitro Extreme Drug Resistance (EDR) assay.
Methods: Outcomes for newly diagnosed ovarian cancer patients with tumor specimens submitted in a serial fashion for the EDR assay were studied. EDR assay results for cisplatin and carboplatin were correlated with clinical outcome for 79 evaluable chemotherapy naive cases who presented with advanced (stages IIC, III, and IV) ovarian cancer. Stage IV and suboptimally debulked stage IIIc accounted for 16 cases, while 63 cases were optimally debulked Stage III/IIc. All patients were treated with platinum-based combination chemotherapy at a single institution. In vitro results for patient tumors were classified as low drug resistance (PCI > median), intermediate drug resistance [PCI between the median and 1 standard deviation (SD) below the median], or extreme drug resistance (PCI more than 1 SD below the median). For the purpose of this analysis, in vitro EDR to either cisplatin or carboplatin was considered to represent extreme resistance to platinum (EDRP), while the absence of EDR to either cisplatin or carboplatin was considered to represent low resistance to platinum (LDRP). Patients demonstrating relative in vitro resistance to paclitaxel and non-cross-resistance to cyclophosphamide and/or doxorubicin received cyclophosphamide plus platinum (CP); cyclophosphamide, doxorubicin, and platinum (CAP); or platinum alone in place of paclitaxel plus platinum (TP). Progression-free survival (PFS) and overall survival (OS) were correlated with EDR assay results.
Results: Median PFS was 6 months for the 17 cases exhibiting EDRP, compared to 24 months for the 62 cases exhibiting LDRP in vitro [relative risk (RR) 3.78, confidence intervals (CI) 1.82-7.83], adjusted for stage, debulking status, in vitro response to 3-OH-cyclophosphamide, and histological grade. Estimated overall 5-year survival was 19% for patients with tumors showing EDRP, compared to 68% for patients with tumors showing LDRP (RR 2.32, CI 1.06-5.07). Patients treated with CP (n = 20) showed no significant difference in OS compared to patients treated with TP (n = 54), CAP (n = 4), or cisplatin (n = 1) alone. In vitro platinum response remained an independent predictor of PFS and OS in multivariate analyses adjusted for CP versus TP, CAP, or platinum administration, and adjusted for debulking status. Median PFS for all 79 patients was 22 months, with an estimated 5-year survival of 57%.
Conclusions: Patients with tumors demonstrating in vitro EDR to platinum were at significantly increased risk for progression and death when treated with standard platinum-based regimens. Such patients may therefore benefit from entry onto trials with novel agents or combinations.

5. Survival outcomes in patients with recurrent ovarian cancer who were treated with chemoresistance assay-guided chemotherapy.

Am J Obstet Gynecol. 2003 Nov;189(5):1301-7.

Loizzi V, Chan JK, Osann K, Cappuccini F, DiSaia PJ, Berman ML.

Objective: The purpose of this study was to determine the outcome of patients with recurrent ovarian carcinoma after extreme drug resistance assay-directed therapy.
Study Design: Fifty women who were treated with chemotherapy based on extreme drug resistance assay guidance were compared with 50 well-balanced control subjects who were treated empirically.
Results: In the platinum-sensitive group, patients with extreme drug resistance-directed therapy had an overall response rate of 65% compared with 35% in the patients who were treated empirically (P=.02). The overall and progression-free median survival were 38 and 15 months in the extreme drug resistance assay group compared with 21 and 7 months in the control group, respectively (P=.005, overall; P=.0002, progression free). In the platinum-resistant group, there was no improved outcome in the patients who underwent assay-guided therapy. In multivariate analysis, platinum-sensitive disease, extreme drug resistance-guided therapy and early stage of disease were independent predictors for improved survival.
Conclusion: In this retrospective analysis, our results indicate an improved outcome in patients with recurrent ovarian carcinoma who have platinum sensitive disease and who underwent extreme drug resistance-directed chemotherapy. Randomized, prospective, controlled trials are needed.

6. A prospective blinded study of the predictive value of an extreme drug resistance assay in patients receiving CPT-11 for recurrent glioma.

J Neurooncol. 2004 Feb;66(3):365-75.

Parker RJ, Fruehauf JP, Mehta R, Filka E, Cloughesy T.

This adjunct to a prospective phase II blinded study of 48 patients with recurrent malignant glioma evaluated the predictive reliability of an extreme drug resistance (EDR) to identify clinical resistance to irinotecan (CPT-11), using fresh tumor biopsies obtained from recurrent patients immediately prior to their first dose of CPT-11 therapy. In vitro tumor response to SN38 (bioactive species of CPT-11 used in the EDR assay) determined prior to treatment was correlated with objective response, time to tumor progression (TTP) and survival following the administration of CPT-11. SN38 activity was tested in 19 of 29 tumors, with 15 of 18 assay results evaluable for correlation with clinical outcomes. In vitro drug resistance was classified as either extreme, intermediate (IDR), or low (LDR). TTP and survival were estimated by the Kaplan-Meier method, and compared using the Mantel-Haenszel log-rank and Fisher's exact test statistics. In vitro tumor response was bifurcated into either EDR (n = 4) or IDR/LDR (n = 11) categories for comparison with outcomes. Results correlated significantly with both TTP and survival. Median TTP for IDR/LDR cases was 3 months versus 6 weeks for EDR cases (log-rank test; p = 0.0288, hazards ratio = 3.06). A 13-week median survival for EDR cases was significantly shorter compared to 38 weeks for IDR/LDR cases (p = 0.029). Further, 100-day survival favored the IDR/LDR cases (Fisher's exact test; p = 0.008). At last follow-up, two of three survivors were patients who had tumors IDR/LDR to SN38. These prospective data support the notion that patients should avoid agents to which their tumor demonstrates EDR.

7. Differences of chemoresistance assay between invasive micropapillary/low-grade serous ovarian carcinoma and high-grade serous ovarian carcinoma.

Int J Genecol Cancer 2007. 2007 May-Jun; 17(3):601-6.

Santilian A, Kim YW, Zahurak ML, Gardner GJ, Giuntoli RL, Shih IM, Bristow RE.

The objective of this study was to evaluate the pattern of chemoresistance in invasive micropapillary/lowgrade serous ovarian carcinoma (invasive MPSC/LGSC) and high-grade serous ovarian carcinoma (HGSC) according to extreme drug resistance assay testing. Surgical specimens of 44 recurrent ovarian cancer patients harvested at the time of cytoreductive surgery between August 1999 and February 2004 were identified retrospectively from the tumor registry database. Thirteen patients (29.5%) had recurrent invasive MPSC/LGSC and 31 (70.5%) patients had recurrent HGSC. Eight drugs were evaluated; extreme drug resistance assay results were compared between LGSC and HGSC groups using Fisher exact tests and exact logistic regression models. Compared to HGSC, invasive MPSC/LGSC were more likely to manifest EDR to the drugs paclitaxel (69% vs 14%, P , 0.001), carboplatin (50% vs 17%, P = 0.05), cyclophosphamide (40% vs 23%, P = 0.41), gemcitabine (36% vs 19%, P = 0.40), and cisplatin (33% vs 28%, P = 0.72) and less likely to be resistant to etoposide (0% vs 44%, P = 0.007), doxorubicin (8% vs 45%, P = 0.03), and topotecan (8% vs 21%, P =0.65). Exact logistic regression estimates revealed that invasive MPSC/LGSC patients had significantly increased probabilities of paclitaxel resistance odds ratio (OR) = 12.5 (95% CI: 2.3-100.0), P = 0.001 and carboplatin resistance OR = 4.8 (95% CI: 0.9-25.0), P = 0.07, while the HGSC cases were more likely to be resistant to etoposide OR = 12.1 (95% CI: 1.7-N), P =0.009 and doxorubicin OR = 8.6 (95% CI: 1.0-413.7), P = 0.05. In this retrospective analysis, patients with recurrent invasive MPSC/LGSC were more likely to manifest EDR to standard chemotherapy agents (platinum and paclitaxel). These observations may help to guide chemotherapeutic decision making in these patients if confirmed in a large-scale study.

8. Extreme drug resistance is common after prior exposure to paclitaxel.

Gynecol Oncol. 2007 Sep;106(3):538-540.

Geisler JP, Linnemeier GC, Thomas AJ, Manahan KJ.

Objective: The platinum-free interval (PFI) is an important entity in the treatment of women with epithelial ovarian cancer. The purpose of this study was to determine on clinical samples whether a taxane-free interval (TFI), as defined by in vitro extreme drug resistance assay, existed in women previously exposed to platinum and taxane chemotherapy.
Methods: Records were examined from 2003 to 2006 to find all patients with epithelial ovarian cancer who had previous exposure to platinum and taxane therapy. Further examination was done to find all patients who underwent secondary cytoreduction and had their tumor submitted for extreme drug resistance assay.
Results: Thirty-four women meeting the above criteria were found. The mean PFI was 25 months (median 18). The mean TFI was 27 months (median 20). Over 44% of the patients have been exposed to more than just a course of platinum and a course of a taxane. In patients having a PFI of =12 months, 38.8% had extreme drug resistance (EDR) to carboplatin and 41.9% EDR to cisplatin. Conversely, in patients having a TFI of =12 months, 89.7% had EDR to paclitaxel and 82.8% EDR to docetaxel.
Conclusions: While only a small percentage have EDR to carboplatin and cisplatin after a PFI of =12 months, almost 90% of patients with a TFI =12 months showed EDR to paclitaxel in vitro.

9. In vitro extreme drug resistance assay to taxanes or platinum compounds for the prediction of clinical outcomes in epithelial ovarian cancer: a prospective cohort study.

 Journal of Cancer Research and Clinical Oncology. 2009 Nov;135(11):1513-20.

Kim HS, Kim TJ, Chung HH, Kim JW, Kim BG, Park NH, Song YS, Bae DS, Kang SB.

Purpose: We sought to investigate the efficacy of in vitro extreme drug resistance assay for the prediction of drug response, platinum-resistance (progression-free survival, PFS < 6 months) and survival in patients with epithelial ovarian cancer (EOC) who received taxane- and platinum-based chemotherapy after surgery.
Methods: Between December 2005 and August 2007, 43 patients were enrolled prospectively. They underwent staging laparotomy followed by six or nine cycles of taxaneand platinum-based chemotherapy, and their tumors were submitted for in vitro EDR assay to taxanes (paclitaxel or docetaxel) and platinum compounds (carboplatin or cisplatin).
Results: The rates of EDR to taxanes and platinum compounds were 20.9% (9/43) and 23.3% (10/43). Patients with EDR to platinum compounds showed a lower rate of overall response (60 vs. 100%), a higher rate of platinumresistance (50 vs. 18.2%) and poor overall survival (OS) (median OS; 29.2 vs. 33.7 months) than those without EDR to platinum compounds (P < 0.05), whereas patients with EDR to taxanes showed poor PFS than those without EDR to taxanes (12.5 vs. 19 months, P < 0.01). Moreover, suboptimal debulking surgery and EDR to taxanes were poor prognostic factors for PFS (adjusted hazard ratio 3.215 and 3.984; 95% conWdence interval 1.845-7.895 and 3.814-11.674, respectively) although there was no independent risk factor for poor OS by the multivariate Cox's proportional hazard analysis.
Conclusions: In vitro EDR assay to taxanes and platinum compounds may be helpful for predicting drug response, platinum-resistance and survival in patients with EOC who received taxane- and platinum-based chemotherapy after staging laparotomy.

10. Low drug resistance to both platinum and taxane chemotherapy on an in vitro drug resistance assay predicts improved survival in patients with advanced epithelial ovarian, fallopian and peritoneal cancer.

 International Journal of Cancer. 2009 Dec 1;125(11):2721-7.

Matsuo K, Bond V, Eno ML, Im DD, Rosenshein NB.

The objective of this study was to evaluate the role of an in vitro drug resistance assay to platinum and taxane in the management of advanced epithelial ovarian, fallopian and primary peritoneal cancer. All patients with FIGO Stage IIIc and IV who received postoperative chemotherapy with platinum and taxane for more than 4 courses after the initial cytoreductive surgery between 1995 and 2008 were evaluated. Patients who received neoadjuvant
chemotherapy were not included. An in vitro drug resistance assay (EDR Assay, Oncotech, Tustin, CA) was used to determine drug resistance for each patient's tumor tissue. Level of drug resistance was described as extreme (EDR), intermediate (IDR), or low (LDR). Response to chemotherapy and survival were correlated to the EDR Assay. Of the 335 patients who underwent primary cytoreductive surgery, 173 cases met the criteria for statistical evaluation. The 58 patients (33.5%) whose tumors had LDR to both platinum and taxane had statistically improved progressionfree survival and overall survival (OS) compared with the 115 patients (66.5%) who demonstrated IDR or EDR to platinum and/ or taxane (5-year OS rates, 41.1% vs. 30.9%, p 5 0.014). The 5-year OS rates for the 28 (16.2%) cases that had optimal cytoreduction with LDR to both platinum and taxane was significantly improved over the 62 (35.8%) cases that were suboptimally cytoreduced with IDR or EDR to platinum and/or taxane (54.1% vs. 20.4%, respectively, p < 0.001). In conclusion, LDR to both platinum and taxane chemotherapy, as determined by an in vitro drug resistance assay, independently predicts improved survival in patients with advanced epithelial ovarian, fallopian and peritoneal cancer, especially in those patients who undergo optimal primary cytoreduction.

11. Chemotherapy time interval and development of platinum and taxane resistance in ovarian, fallopian, and peritoneal carcinomas.

 Archives Gynecology and Obstetrics. 2010 Feb;281(2):325-8.

Matsuo K, Eno ML, Im DD, Rosenheim NB.

Objective: To evaluate drug resistance after exposure to neoadjuvant chemotherapy and to postoperative chemotherapy in epithelial ovarian, fallopian, and primary peritoneal carcinomas.
Methods: In vitro drug resistance assay results (EDR Assay, Oncotech, Inc.) for platinum and taxane were evaluated for the following three groups: (1) primary cytoreductive surgery without prior chemotherapy; (2) primary cytoreductive surgery after neoadjuvant chemotherapy with platinum and taxane; and (3) recurrent cases after postoperative chemotherapy with platinum and taxane. Proportions of extreme drug resistance (EDR) were analyzed with Fisher's exact test.
Results: There were 277 cases that underwent primary cytoreductive surgery without prior chemotherapy: 14 cases of primary cytoreductive surgery after neoadjuvant chemotherapy with platinum and taxane, and 65 recurrent cases. Primary cytoreductive cases following neoadjuvant chemotherapy displayed an increased proportion of EDR to platinum agents compared to primary cytoreductive surgery without prior chemotherapy: neoadjuvant versus non-neoadjuvant, cisplatin 30 versus 7.3%, OR 5.4, 95%CI 1.3-23.2, P = 0.027; carboplatin 33.3 versus 9.2%, OR 4.9, 95%CI 1.4-17.6, P = 0.038. There were no differences in the proportion of EDR to taxanes between the two groups. On the contrary, recurrent cases showed an increased proportion of EDR to paclitaxel compared to primary cytoreductive surgery without prior chemotherapy: recurrent versus primary, paclitaxel 33.3 versus 21.1%, OR 1.9, 95%CI 1.0-3.5, P = 0.031. There were no differences in the proportion of EDR for platinum and docetaxel between the two groups. Among recurrent cases, there was statistical signiffcance between proportion of paclitaxel EDR and time interval of initial and recurrent surgeries (R2 0.143, P = 0.011). Recurrent surgery after 5 years from initial cytoreduction was signiWcantly associated with increased proportion of EDR to paclitaxel: 61.5 versus 22.6%, OR 5.5, 95%CI 1.35-22.2, P = 0.011.
Conclusions Platinum resistance was common after neoadjuvant chemotherapy, while paclitaxel resistance was common after postoperative chemotherapy.

12. Survival among patients with platinum resistant, locally advanced non-small cell lung cancer treated with platinum-based systemic therapy.

 Annals of Surgical Oncology. 2009 Oct;16(10):2848-55.

D'Amato TA, Pettiford BL, Schuchert MJ, Parker PJ, Ricketts WA, Luketich JD, Landreneau RJ.

Background. Recent adjuvant chemotherapy trials after resection of stage II and III non-small cell lung cancer (NSCLC) have identified important survival differences among patients with immunohistochemical evidence suggesting platinum resistance. No clinical information exists regarding the impact upon survival of patients treated with platinum agents who exhibit cellular evidence of their tumors' resistance to platinum. We evaluated the utility of the extreme drug resistance (EDR) assay to predict mortality among a consecutive group of stage II through IV NSCLC patients receiving adjuvant or definitive platinumbased chemotherapy after resection or surgical biopsy.
Methods. The Extreme Drug Resistance (EDR) Assay is a clinically validated cellular proliferation assay used to test tumors for chemotherapy drug resistance. Based on response in the EDR assay, tumor specimens from stage II through IV NSCLC patients were segregated into three groups: extreme drug resistant (EDR), intermediate drug resistant (IDR), and low drug resistant (LDR). Patient survival was evaluated after platinum-based chemotherapy.
Results. Platinum IDR/EDR was statistically significant in predicting shorter overall survival (29.8 months vs. 15.6 months) among platinum IDR/EDR-resistant patients compared with LDR patients (P = 0.047). Median survival was 16.6 months for patients with IDR/EDR to platinum and any other second agent of doublet therapy compared with patients with LDR to any platinum-based doublet where median survival was not achieved (P = 0.0268).
Conclusions. This is the first study to demonstrate the utility of the EDR assay to predict poor clinical outcome when platinum-based therapy is used to treat patients with biological evidence of tumor resistance to platinum. These data corroborate the finding of recent studies evaluating possible molecular correlates to poor response to specific chemotherapeutic agents.

13. Efficacy of taxane and platinum-based chemotherapy guided by extreme drug resistance assay in patients with epithelial ovarian cancer.

 J Gynecol Oncol. 2009 June; 20(2):96-100.

Joo WD, Lee JY, Kim JH, Yoo HJ, Roh HJ, Park J-Y, Kim D-Y, Kim Y-M, Kim Y-T, Nam J-H.

Objective: To evaluate the efficacy of taxane and platinum-based chemotherapy guided by extreme drug resistance assay (EDRA) in patients with epithelial ovarian cancer.
Methods: Thirty-nine patients were enrolled, who were diagnosed as epithelial ovarian cancer, tubal cancer or primary peritoneal carcinoma and received both debulking surgery and EDRA in Asan Medical Center between August 2004 and August 2006. Another thirty-nine patients were enrolled, who did not receive EDRA as control. Paclitaxel 175mg/m2 and carboplatin AUC 5 were administered as primary combination chemotherapy to both EDRA group and the control group. In the EDRA group, paclitaxel was replaced by docetaxel 75 mg/m2 if a patient showed extreme drug resistance (EDR) to paclitaxel and not to docetaxel. Carboplatin was replaced by cisplatin 75 mg/m2 if a patient showed EDR to carboplatin and not to cisplatin. If only one drug showed low drug resistance (LDR), it was allowed to add another drug which showed LDR such as gemcitabine 1,000 mg/m2. CT scan was performed every three cycles and CA-125 was checked at each cycle.
Results: There was no significant difference in overall response rate between EDRA group and the control group (84.5% vs. 71.8%, p=0.107). However, 93.8% of patients in EDRA group did not show EDR to at least one drug and its response rate was significantly higher than that of the control group (93.3% vs. 71.8%, p=0.023).
Conclusion: we could choose a combination of taxane and platinum which did not show EDR and could obtain a good response in the patients with ovarian cancer.

14. Extreme drug resistance for carboplatin predicts resistance to first-line therapy in advanced-stage ovarian cancer: results from the EORTC-CGC/NCIC-CTG neoadjuvant trial.

 Bangkok, Thailand, October 25-28, 2008

L. Verleye (1), C. Coens (1), F. Amant (2), M.E.L. van der Burg (3), N. Johnson (4), R. Verheijen (5), A. Casado (6), N.S. Reed (7), R.J. Parker (8), I. Vergote (2)

(1) EORTC Headquarters, EORTC-GCG, Brüssel, Belgien,
(2) UZ-Leuven, Department of Gynaecological Oncology, Division Obstetrics & Gynaecology, Leuven,
(3) Erasmus MC, University Medical Center Rotterdam, Department of Medical Oncology, Rotterdam,
(4) Royal United Hospital, Department of Obstetrics and Gynaecology, Bath, Großbritannien,
(5) VUmc / UMCU Amsterdam / Utrecht, Niederlande,
(6) Hospital Universitario San Carlos, Department of Medical Oncology, Madrid, Spanien,
(7) Beatson Oncology Centre, Gartnavel General Hospital, Glasgow, Großbritannien,
(8) Oncotech Inc., Irvine, USA

Introduction: The EORTC 55971/NCIC OV13 trial included 719 patients with stage IIIc-IV
epithelial ovarian cancer who all received platinum-based chemotherapy. Patients were randomizedto primary or interval debulking surgery. More than one third of included patients appeared to be platinum resistant (progression during or within 6 months after first-line chemotherapy). A predictive test identifying patients' resistance to standard treatment would allow for more individualized treatment, including non-platinum based chemotherapy. We therefore investigated if the Extreme Drug Resistance (EDR) Assay (Oncotech - Exiqon AS Copenhagen) could predict resistance to platinum-based chemotherapy.
Patients and methods: Tumor tissue biopsies were taken during cytoreductive surgery and tested with the EDR assay against 11 chemotherapeutic agents, including carboplatin and paclitaxel. In vitro drug resistance was based on the percentage of chemotherapy induced cell growth inhibition. Clinical response to first line treatment was assessed according to the RECIST criteria.
Results: Biopsies were obtained from 246 patients. EDR based resistance to cisplatin and topotecan showed a positive relationship with WHO performance status; resistance to gemcitabin was positively linked to FIGO stage (p< 0.05). In vitro EDR to carboplatin showed a significant association with resistance to first-line treatment (p< 0.05). Multivariate analysis revealed residual disease after surgery (p < 0.0001), number of chemotherapy cycles received (p = 0.007) and EDR to carboplatin (p = 0.008) as independent predictors of response.
Conclusion: EDR to carboplatin was an independent significant predictive factor for failure of response to first-line platinum-based treatment in advanced ovarian cancer.

Validation Studies

1. Heterogeneity of drug resistance in human breast and ovarian cancers.

 Cancer J Sci Am. 1998 Jan-Feb;4(1):41-5.

Kern DH.

PURPOSE: This study quantitates the extent of heterogeneity of drug resistance in breast and ovarian cancers. Identification of drug-specific resistance in tumors from multiple sites provides information necessary to understand the unique biology of a patient's disease.
MATERIALS AND METHODS: Drug resistance to cisplatin, paclitaxel, and doxorubicin was measured in multiple synchronous or metachronous tumors using the extreme drug resistance (EDR) assay. The degree of resistance for each tumor was classified into one of three categories: low drug resistance (LDR), EDR, or intermediate drug resistance (IDR).
RESULTS: When tested against cisplatin, 66% of primary ovarian cancers and their paired synchronous distant metastases (N = 88) shared the same resistance category, while 4% of the results were discordant (one site had EDR and the other site had LDR). Of the paired results for paclitaxel (N = 68), 54% were in the same resistance category, while 13% of the comparisons were discordant. Heterogeneity of drug response to cisplatin was also measured in primary ovarian cancers and paired recurrent tumors from 108 women. Median time to recurrence was 9.6 months. Only 55% of the paired results fell into the same resistance category, while 19% of the results were discordant. Drug resistance to doxorubicin was measured in primary breast cancers and paired synchronous metastases from 23 women: 74% of the paired results fell into the same resistance category, while 13% of the results were discordant. Metastatic sites had a slightly higher incidence of EDR than primary sites (26% and 17%, respectively). Heterogeneity of drug response to doxorubicin was then determined in primary breast cancers and paired recurrent tumors from 26 women with a median time to recurrence of 14.3 months. Only 52% of the paired results fell into the same resistance category, while 24% of the results were discordant.
DISCUSSION: Heterogeneity of drug resistance for ovarian and breast cancer is a serious clinical problem encountered in administering chemotherapy for overt metastatic or recurrent cancers. The first step in managing this problem is to recognize that heterogeneity of drug resistance exists. Drug resistance tests may then help the physician avoid administering certain chemotherapeutic agents when a patient's metastatic or recurrent tumor is found to be resistant to those agents.

2. Factors associated with success of the extreme drug resistance assay in primary breast cancer specimens

 Breast Cancer Res Treat. 2002 Jan;71(2):95-102.

Ellis RJ, Fabian CJ, Kimler BF, Tawfik O, Mayo MS, Decelis CR, Jewell WR, Connor C, Modrell C, Praeger M, McGinness M, Mehta R, Fruehauf JP.

The extreme drug resistance (EDR) assay has not been widely studied in the setting of non-metastatic breast cancer. We evaluated the feasibility of performing the assay in 144 primary breast tumor specimens from two institutions by determining the rate of successful tumor culture for assays, number of drugs evaluated per assay, and time from tumor biopsy to receipt of results. We also sought to determine factors that are associated with assay success. An exploratory analysis was performed to detect possible associations between estrogen receptor (ER), progesterone receptor (PR) and HER2/NEU over-expression and extreme drug resistance demonstrated by the assay for specific chemotherapeutic agents. Of 144 tumor specimens submitted, tumor was successfully cultured for assay in 101(70%) of cases. A median of five drugs was evaluated per assay (range 2-9). Results were obtained in a median of 8 days (range 2-29). Young age, high tumor grade, PR negativity, and higher tumor submission weight were predictive for a successful assay. EDR was observed in 7-15% of tumors to doxorubicin, cyclophosphamide, 5-fluorouracil (5FU) and mitoxantrone, but EDR to paclitaxel was observed in 35%. Extreme drug resistance to 5-FU was associated with negative ER and PR status. There was a trend toward association between EDR to paclitaxel and HER2/NEU over-expression. The der assay may be successfully performed in the majority of tumors, and assay results are available in a timely fashion such that adjuvant treatment drug selection could be guided by results. These results may be helpful for designing possible future trials that evaluate the assay's role in adjuvant chemotherapy selection.

3. Extreme drug resistance in primary brain tumors: in vitro analysis of 64 resection specimens.

 J Neurooncol. 2002 Jun;58(2):115-23.

Haroun RI, Clatterbuck RE, Gibbons MC, Burger PC, Parker R, Fruehauf JP, Brem H.

Understanding chemoresistance profiles of brain tumors may aid in more educated selection of chemotherapeutic regimens for clinical trials and patient treatment. Although the literature contains many reports of the application of drug resistance assays, little is known about extreme drug resistance (EDR) in primary brain tumors. We undertook this study to determine chemoresistance profiles for brain tumors. From September 1991 to February 1998, we collected 64 brain tumor specimens from patients admitted to the Johns Hopkins Hospital. Tumors were classified according to the revised World Health Organization system. Brain tumor specimens were tested against 13 different chemotherapeutic agents using an extreme drug resistance assay.
Results were reported as percent cell inhibition (PCI) (compared to control cultures). A drug resistance profile (extreme, intermediate, or low) was determined based on statistical comparison to a historical database of tumor specimens tested against the same panel of chemotherapeutic agents. Brain tumor specimens were classified histologically as Grade IV astrocytoma (glioblastoma multiforme, n = 35), Grade II/III astrocytoma (n = 11), oligodendroglioma (n = 6), meningioma (n = 9), hemangiopericytoma (n = 2), and ependymoma (n = 1). A large percentage of glioblastomas displayed extreme drug resistance to paclitaxel (69%, n = 35), SN38 (75%, n = 28), and vincristine (38%, n = 29). The majority of Grade II/III astrocytomas displayed extreme drug resistance to carboplatin (67%, n = 6), cisplatin (60%, n = 10), and paclitaxel (60%, n = 10). In a similar fashion, oligodendrogliomas displayed extreme drug resistance to vincristine (60%, n = 5) and paclitaxel (50% n = 6). Most meningiomas displayed extreme drug resistance to vincristine (75%, n = 8), dacarbazine (63%, n = 8), and 4-HC (50%, n = 8). Through the continued analysis of brain tumor specimens and compilation of data from multiple institutions, chemoresistance profiles could assist in the development of rationale clinical trials and treatment regimens for patients with brain tumors.

4. In vitro chemoresistance and biomarker profiles are unique for histologic subtypes of epithelial ovarian cancer.

 Gynecol Oncol. 2004 Jan;92(1):160-6.

Cloven NG, Kyshtoobayeva A, Burger RA, Yu IR, Fruehauf JP.

OBJECTIVES: To determine whether there is a relationship between histologic subtype of epithelial ovarian cancer and chemoresistance, we evaluated ovarian carcinomas of six histologic subtypes and correlated histology with in vitro drug response. Biomarker profiles (p53, Her-2 neu, and EGFR) were also evaluated to determine if their expression patterns were associated with histology.
METHODS: In vitro drug response profiles for different histologic subsets of epithelial ovarian carcinomas exposed to standard relevant chemotherapy agents were determined in the Extreme Drug Resistance assay (EDR). Immunohistochemistry techniques were employed to determine biomarker expression.
RESULTS: Of 5195 referred serial cases of epithelial ovarian cancer, there were 2660 papillary serous, 303 endometrioid, 142 mucinous, 102 clear cell, 952 undifferentiated carcinomas, and 42 tumors of low malignant potential. For the samples as a whole, the incidences of extreme drug resistance to the tested chemotherapeutic agents were cisplatin 10%, carboplatin 16%, cyclophosphamide 16%, doxorubicin 40%, gemcitabine 21%, paclitaxel 22%, and topotecan 13%. When compared to papillary serous tumors, mucinous tumors were more frequently resistant to cisplatin (10% vs. 18%) but less frequently resistant to topotecan (13% vs. 5%) and doxorubicin (42% vs. 16%). Endometrioid tumors were less resistant to cisplatin (10% vs. 6%) and doxorubicin (42% vs. 20%). Clear cell and undifferentiated tumors had the lowest rates of EDR to paclitaxel (13% and 18%) and cyclophosphamide (7% and 11%), while borderline tumors showed high rates of EDR to these agents (52% and 63%, respectively). With respect to biomarker profiles, mP53 was detected in 46%, Her-2 neu in 16%, and EGFR in 30% of the cases evaluated. As compared to all other subtypes, clear cell carcinomas had significantly higher Her-2 neu expression (19%). Relative to papillary serous carcinomas, borderline tumors exhibited significantly lower rates of mP53 expression (60% vs.17%).
CONCLUSIONS: We found significant differences in the frequencies of extreme drug resistance to chemotherapeutic agents and biomarker expression among histologic subtypes of epithelial ovarian cancer. The data collected in this investigation may provide a guide for stratification of patients entering clinical trials based on histology and biomarker expression.

5. Conservation of in vitro drug resistance patterns in epithelial ovarian carcinoma.

 Gynecol Oncol. 2005 Sep;98(3):360-8.

Tewari KS, Mehta RS, Burger RA, Yu IR, Kyshtoobayeva AS, Monk BJ, Manetta A, Berman ML, Disaia PJ, Fruehauf JP.

PURPOSE: To compare the in vitro drug resistance profiles of advanced stage primary and recurrent epithelial ovarian cancer specimens using the tritiated thymidine uptake assay.
METHODS: Extreme drug resistance (EDR) to cisplatin, paclitaxel, 4-hydroxycyclophosphamide, and topotecan was determined for an unselected population of primary and metastatic malignant ovarian tissues, synchronous tumors (primary and metastatic tissues obtained from the same patient at diagnosis), and metachronous lesions (specimens from the same patient before and after chemotherapy).
RESULTS: For the large unselected population of malignant tissues (total, N = 6990; primary ovarian, N = 2031; metastatic ovarian, N = 4959), no statistically significant differences were discovered between primary tissues and metastatic lesions when a comparison was made between the percentage of tumors from each group that exhibited extreme drug resistance to the agents assayed. From the library of 6990 specimens, 119 synchronous pairings were identified. These synchronous lesions did not differ significantly in the %EDR between primary and metastatic sites in the same patient; approximately 10% shifted between low drug resistance and EDR. A total of 334 metachronous pairings were identified and the percentage of tissues that exhibited EDR also failed to show a significant difference when primary tumors were compared with matched recurrences in the same patient.
CONCLUSIONS: For the agents studied, acquired resistance was not a function of disease site. In vitro drug resistance observed at recurrence was not influenced significantly by intervening therapy. It is possible that assay results at diagnosis could be used to guide subsequent therapy at relapse, especially when recurrent tissue is not available for analysis.

6. Prevalance of in vitro extreme chemotherapy resistance in resected non-small cell lung cancer.

 Annals of Thoraic Surgery, 2006, 81: 440-447.

D'Amato TA, Landreneau RJ, McKenna RJ, Santos RS, Parker RJ

Background. Recent clinical trials suggest that adjuvant chemotherapy provides a survival advantage for patients with completely resected nonsmall-cell lung cancer (NSCLC) yet many patients receive chemotherapy without benefit. Tumor in vitro resistance to antineoplastic agents is highly predictive of clinical unresponsiveness to chemotherapy for some cancers; however, little is known of the prevalence of extreme chemotherapy drug resistance for human NSCLC tumors. Chemoresistance testing may be a way to predict treatment failure, choose alternative agents, and to avoid unnecessary chemotherapy toxicity. This study describes the prevalence of in vitro chemotherapy resistance in NSCLC patient tumor cultures.
Methods. A total of 3,042 NSCLC specimens were cultured in a proliferation assay and tested for resistance to carboplatin, cisplatin, doxorubicin, etoposide, gemcitabine, navelbine, paclitaxel, taxotere, or topotecan. The percentage of cell-growth inhibition measured by 3Hthymidine uptake was used to determine extreme drug resistance, intermediate drug resistance, or low drug resistance.
Results. Extreme drug resistance or intermediate drug resistance to carboplatin was found in 1,056 of 1,565 NSCLC cultures (68%), to cisplatin in 1,409 of 2,227 (63%), to doxorubicin in 1,101 of 1,471 (75%), to etoposide in 1,581 of 2,505 (63%), to gemcitabine in 594 of 823 (72%), to navelbine in 603 of 1,444 (42%), to paclitaxel in 689 of 1,706 (40%), to taxotere in 273 of 521 (52%), and to topotecan in 280 of 896 (31%). Conclusions. Chemotherapy resistance is prevalent among NSCLC clinical cell cultures. This may account for the small survival seen with empiric adjuvant chemotherapy. The use of viable tumor culture for in vitro chemoresistance testing should be considered when formulating a plan of adjuvant therapy for resected NSCLC. Future trials comparing patient survival after tailored versus empiric adjuvant therapy appear justified.