Correlation between Extreme Drug Resistance Assay and Response to Primary Paclitaxel and Cisplatin in Patients with Epithelial Ovarian Cancer

Abstract Objective. The extreme drug resistance (EDR) assay has been correlated with failure of response to chemotherapy in greater than 99% of patients. The goal of this study is to correlate the results of the EDR assay to response to first-line paclitaxel/cisplatin among patients with epithelial ovarian cancer. Methods. Seventy-five of 100 patients with epithelial ovarian cancer for whom EDR assay was performed were treated with weekly induction cisplatin (1 mg/kg body wt) × 4, followed by monthly paclitaxel (135 mg/m 2 ) and cisplatin (75 mg/m 2 ) × 6 and were evaluable for correlation of response to chemotherapy and EDR assay. Specimens for EDR assay were obtained at primary surgery and the EDR assay was performed by Oncotech, Inc. Response to chemotherapy was correlated to EDR assay results regarding paclitaxel and cisplatin. Results. Among 75 evaluable patients, the prevalence of EDR to paclitaxel was 20.0% ( n = 15) and to cisplatin it was 2.7% ( n = 2). Only 1 patient (1.3%) exhibited EDR to both paclitaxel and cisplatin. Surgical assessment of response was performed in 42 patients; 33 patients were clinically evaluable. The overall response rate was 85.3%. The overall response rate for patients whose tumors demonstrated no EDR to either paclitaxel or cisplatin did not differ significantly from that for patients whose tumors demonstrated EDR to at least one of these two drugs (86.4% versus 81.3%, respectively, P = 0.692). Similarly, the complete surgical response rate for both groups did not differ significantly (25.4% versus 12.5%, respectively, P = 0.34). A single patient whose tumor exhibited EDR to both paclitaxel and cisplatin had tumor progression. The sensitivity, specificity, positive predictive value, and negative predictive value of the EDR assay were 79.6, 27.0, 86.0, and 19.0%, respectively. Conclusions. EDR to paclitaxel does not preclude response to the combination of paclitaxel and cisplatin as primary therapy for patients with epithelial ovarian cancer. The role of the EDR assay in the primary management of patients with epithelial ovarian cancer remains to be determined.