Background: The impact of primary tumor location on overall survival (OS), recurrence-free survival (RFS), and long-term outcomes has not been well established in patients undergoing potentially curative resection of colorectal liver metastases (CRLM).
Methods: A single-institution database was queried for initial resections for CRLM 1992-2004. Primary tumor location determined by chart review (right = cecum to transverse; left = splenic flexure to sigmoid). Rectal cancer (distal 16 cm), multiple primaries, and unknown location were excluded. Kaplan-Meier and Cox regression methods were used. Cure was defined as actual 10-year survival with either no recurrence or resected recurrence with at least 3 years of disease-free follow-up.
Results: A total of 907 patients were included with a median follow-up of 11 years; 578 patients (64%) had left-sided and 329 (36%) right-sided primaries. Median OS for patients with a left-sided primary was 5.2 years (95% confidence interval [CI] 4.6-6.0) versus 3.6 years (95% CI 3.2-4.2) for right-sided (p = 0.004). On multivariable analysis, the hazard ratio for right-sided tumors was 1.22 (95% CI 1.02-1.45, p = 0.028) after adjusting for common clinicopathologic factors. Median RFS was marginally different stratified by primary location (1.3 vs. 1.7 years; p = 0.065). On multivariable analysis, location of primary was not significantly associated with RFS (p = 0.105). Observed cure rates were 22% for left-sided and 20% for right-sided tumors.
Conclusions: Among patients undergoing resection of CRLM, left-sided primary tumors were associated with improved median OS. However, long-term survival and recurrence-free survival were not significantly different stratified by primary location. Patients with left-sided primary tumors displayed a prolonged clinical course suggestive of more indolent biology.