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Background: In colorectal cancer, the involvement of regional lymph nodes with metastasis is an established prognostic factor. However, the impact of the number of positive regional nodes on patient outcome with stage IV disease is not well-defined.
Methods: A retrospective review was performed of 869 patients at two tertiary referral centers with synchronous stage IV colorectal cancer who underwent resection of their primary tumors. Associations between number of positive regional lymph nodes stratified by the 7th edition AJCC staging system, lymph node ratio (LNR), and overall survival (OS) from date of diagnosis were analyzed. Median follow-up was 19 months (range, 1-211 months).
Results: The number of positive regional nodes and LNR correlated with the presence of multiple sites of distant metastases (p<0.001). Survival was significantly associated with number of positive nodes and LNR, with median OS of 36 months with negative regional nodes, compared to 17 months with >/= 7 positive nodes (p<0.001). Among 315 patients treated with modern oxaliplatin- or irinotecan-based chemotherapy after colorectal resection, survival was not significantly associated with number of positive regional nodes (p=0.072) or LNR (p=0.34). The number of regional nodal metastases correlated with OS among 249 patients who underwent resection of liver metastases but lost prognostic significance in the subset of 105 patients who underwent hepatectomy with perioperative modern chemotherapy.
Conclusions: In stage IV colorectal cancer, increasing number of positive regional lymph nodes and LNR correlate with multiple sites of distant metastases and poorer survival. The number of metastatic regional lymph nodes loses prognostic significance with modern chemotherapy, particularly in patients undergoing resection of liver metastases.