Primary tumor location and survival in general population with metastatic colorectal cancer (mCRC).

Abstract

674 Background: Recent evidence from clinical trials suggests that location of the primary tumor in patients with mCRC correlates with differential outcomes and patients with tumors originating in the right side of colon have inferior survival. This large population-based cohort study using individual patient data was performed to confirm this findings in general population with mCRC. Methods: A cohort of 1947 patients who were diagnosed with synchronous mCRC from 1992-2010 was studied. Ascending and transverse colon cancers were defined as right-sided tumors (RT) and remainder tumors were define as left-sided tumors (LT). Cox proportional multivariate analyses were done to determine prognostic significance of primary tumor location and to adjust other prognostic variables including age, Charlson comorbid index (CCI) and WHO performance status (PS) in patients treated with chemotherapy. Results: Median age was 70 years (IQR: 60-78) and M:F was 1.3:1. Mean CCI was 9.7±1.4 and 29% had WHO PS of > 1. 770 (39%) patients had RT and 37% had stage IVb disease. 908 (47%) received chemotherapy and of those 44% received modern chemotherapy. Significant differences were noted between the groups with RT and LT with respect to age, WHO PS, CCI, liver metastases, mucinous tumor, grade, smoking history, and primary tumor resection. Median overall survival of patients with RT was 14 (95%CI: 12.7-15.3) months compared with 20.5 (95%CI: 18.5-22.5) of patients with LT (p < 0.001). On multivariate analysis following variables were correlated with inferior survival: Right-sided tumors, hazard ratio (HR) 1.40 (95%CI: 1.20-1.60); no primary tumor resection, HR 1.60 (95%CI: 1.32-1.90); no metastasectomy, HR 2.40 (95%CI: 1.90-2.90); not using modern chemotherapy, HR 1.52 (95%CI: 1.31-1.80); leukocytosis, HR 1.44 (95%CI: 1.28-1.73); elevated CEA, HR 1.54 (95%CI: 1.30-1.90); WHO PS > 1, HR 1.30 (95%CI: 1.10-1.55); and stage IVb disease, HR 1.50 (95%CI: 1.17-1.86). Tests for interaction were negative. Conclusions: Our results confirm that patients with RT who received chemotherapy have inferior survival independent of other known prognostic variables. Future studies are required to understand underlying pathophysiology.