Analyses of Multiple Factors for Determination of "Selected Patients" Who Should Receive Rechallenge Treatment in Metastatic Colorectal Cancer: a Retrospective Study from Turkey

Background: Repeating a prior chemotherapy (rechallenge therapy) is an option for selected patients with metastatic colorectal cancer, but there is very little evidence in the literature for this approach. Thus, we reviewed our registry to evaluate prognostic factors and survival of patients who received irinotecan and oxaliplatin-based regimens as rechallenge third and fourth-line therapy. Materials and Methods: Patients who received irinotecan-based or oxaliplatin-base regimen as first-line had been rechallenged with third-line or fourth-line therapy. These patients were selected from the database of Turkish mCRC registry archives between October 2006 and June 2013 and evaluated retrospectively for factors effecting progression free survival (PFS) and overall survival (OS) by the Kaplan-Meire and Cox-regression methods. Results: Thirty-nine patients were enrolled. The median duration of follow-up was 36 months (14-68 months). Thirty-one patients (76%) died during follow-up. In terms of rechallenge treatments, 29 patients had received third-line and 10 patients had received fourth-line. Response rate (RR) was found to be 12.9%, with stable disease in 19 (48.7%) patients. The median PFS was 6 months (95%CI=4.64-7.35 months) and the median OS was 11 months (95%CI=8.31-13.68 months). The factors effecting survival (PFS and OS) were only being PFS after first-line chemotherapy ${\geq}12months$ (p=0.007, 95% CI=1.75-35.22 and p=0.004, 95%CI=1.44-7.11), both in univariate and multivariate analyses. Conclusions: This study indicates that rechallenge treatment could be a good option as a third or later line therapy in patients who had ${\geq}12months$ PFS onreceiving first line therapy.