Abstract
742 Background: The anatomical side of the colon where a tumor arises has been shown to be prognostic in patients treated with first-line therapy; patients with tumors that arise from the left side of the colon have significantly longer survival compared with patients whose tumors arise from the right side of the colon. However, there is little evidence of whether this factor is prognostic in later lines of treatment. The objective of this study was to determine the impact of tumor side on the survival of metastatic colorectal cancer patients who received second line (2L) or third line (3L) therapy. Methods: Metastatic (stage IV) colorectal cancer patients in the Surveillance, Epidemiology, and End Results (SEER) database linked to Medicare claims diagnosed 2001-2005 who received 2L (n = 921) or 3L (n = 502) therapy were included in the study. Overall survival (OS) was determined from the start of the indicated line of therapy and was estimated using the Kaplan-Meier method; statistical differences were tested using the log-rank tests. Results: The distribution of tumor sites was similar for 2L and 3L treated patients (right: 36%; left: 58%; transverse: 6%; for 2L). The median follow up time from start of therapy was 11 months (mo) for 2L and 10 mo for 3L patients. Median OS for left-sided tumors receiving 2L+ therapy was 13.6 mo (95%CI: 11.9, 14.8) compared with 8.7 mo (95%CI: 7.5, 9.9) for right-sided tumors (log-rank p < 0.001). Similar results were seen in patients receiving 3L+ therapy, although the difference was of lesser magnitude. The median OS for patients with left-sided tumors was 10.8 mo (95%CI: 9.6, 12.9) compared with 7.6 mo (95%CI: 5.7, 9.4) for right-sided tumors (log-rank p = 0.002). Conclusions: These results suggest that side of tumor origin remains a prognostic factor for colorectal cancer patients treated in later lines of therapy (2L+).
Published Version
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