Correlation of in vitro chemotherapy drug resistance assay to clinical response to carboplatin and paclitaxel combination chemotherapy in ovarian carcinoma.
e16546 Background: Carboplatin sensitivity in drug resistance assays has been shown to be an independent predictor of longer progression free interval with conflicting results in overall survival. We evaluated in vitro drug resistance for carboplatin and paclitaxel combination and its correlation with progression free survival (PFS) and overall survival (OS). Methods: From April 1, 2006 to December 12, 2011, in vitro drug resistance assays were sent after cytoreductive surgery for primary epithelial ovarian cancer. Patients were analyzed according to drug resistance scoring system of low drug resistance (S), intermediate drug resistance (I), and extreme drug resistance (R). Retrospective chart review was performed to evaluate PFS and OS. The Kaplan Meier product limit method was used to estimate OS and PFS. Survival curves were compared between groups using the log rank test. Results: From a total of 142 patients: 57 were S, 52 I, and 33 R; 77% were responsive (S+I) to carboplatin and paclitaxel combination. At median follow-up of 18 months, PFS and OS rates were 58.1 and 91.3% respectively for S, 66.1 and 78.7% for I, and 43.2% and 84.3% for R. At 36 months, the PFS and OS rates were 52.3 and 61.1% for S, 51.3 and 55.3% for I and 39.3% and 48.7% for R. There was OS advantage between the S and I compared to R. There were no significant differences in PFS curves (p<0.281) or OS curves (p<0.46). Conclusions: Although sensitivity to carboplatin/ paclitaxel resulted in longer OS, the results were not statistically significant. Our cohorts were small and we may not have had the power to capture statistical significance. A larger multicenter analysis would be needed to further evaluate this finding. In addition, one of the regimens our patients received on relapse was bevacizumab which was not evaluated in the in vitro assay sensitivity assay. Bevacizumab has also been included in first line treatment in combination with platinum/ taxane regimen. Future analysis of in vitro assays may need to include biologics.