Metastatic Colorectal Cancer Treatment to progression or Not?

Abstract

13511 Background: Treatment until progression or planned interruption of first line chemotherapy is common in the therapy for metastatic colorectal cancer and are upon the discretion of the oncologist. A retrospective analysis was performed to determine the impact of these differing therapeutic strategies on overall survival. Methods: Eligible patients were treated between 2002 to 2004 in British Columbia. All patients received chemotherapy with both FOLFOX and FOLFIRI, either first or second line. Records were retrospectively reviewed for treatment interruption, efficacy and toxicity. Overall survival was the primary endpoint. Results: 101 patients were identified. Twenty-three patients who progressed before receiving 8 cycles of chemotherapy and 9 patients who stopped their chemotherapy due to toxicity were excluded. The remaining patients were analyzed for survival. Twenty-three patients were treated to progression of whom 6 received first line FOLFIRI and 17 received first line FOLFOX. The mean number of cycles of first line therapy was was 11.5. Forty six patients received a planned break. Of these, 21pateints received first line FOLFIRI and 25 patients received first line FOLFOX. Mean number of cycles of first line therapy was 9.7. Median survival of patients treated to progression was 16 months compared to 22 months for patients with planned break of therapy (p=0.003). The Hazard ratio was 2.3 (p=0.01) in favor of patients who had a planned break. Uni-variate and multivariate analysis showed no significance of sex, age, site (colon versus rectal), sequence and ECOG status as predictive factors. Conclusion: In this study, patients who were treated until progression with first line chemotherapy with either FOLFOX or FOLFIRI had an inferior survival. Possible explanations for the detrimental hazard ratio for patients treated to progression are decreasing reserve for second line therapy when first line therapy is prolonged and increasing resistance to 5-FU based therapy with prolonged exposure. As this is a retrospective, observational study, other variables not captured by the modeled covariates that may have influenced results. This data suggests that treating to best response and then allowing a break does not detrimentally affect survival. No significant financial relationships to disclose.