Location of Primary Tumor Impacts Survival After Pulmonary Metastasectomy for Colorectal Cancer

Background: The benefit of pulmonary metastasectomy (PM) in patients with colorectal cancer (CRC) with isolated lung metastases remains unclear and failure to separate colon from rectal cancer may contribute. Utilizing a large national database, we investigate whether PM is associated with survival benefits in patients presenting with CRC with synchronous lung metastases based upon primary tumor location.

Methods: The Surveillance, Epidemiology, and End Results (SEER) database from 2010 to 2015 was queried to identify patients with stage IV CRC with isolated synchronous lung metastases at initial diagnosis. These patients were restricted to include only those where the location of the primary tumor being either colon or rectum could be conclusively identified, and the primary site was resected. SEER-linked Medicare claims were also queried to identify cases of PM that were not adequately recorded in SEER alone. Patients were then analyzed using Kaplan-Meier (K-M) methods and multivariate analysis was performed to identify variables associated with overall survival (OS).

Results: From the SEER database 185,871 metastatic CRC patients were identified. Only 588 had isolated synchronous lung metastases, with 441 with colon cancer and 147 with rectal cancer. PM was performed in 15.3% (n=90) with two-thirds being colon cancer. Univariate K-M demonstrated worse OS for rectal cancer compared to colon cancer, which remained significant on multivariate analysis.

Conclusions: OS is associated with site of primary CRC in patients undergoing PM. Distinct mutational and molecular characteristics differences between colon and rectal cancer may explain these findings and is an area for future research.