Resection of primary tumor in patients who present with stage IV colon cancer may result in improved survival.

726 Background: Resection of the primary cancer in patients with metastatic disease has been shown to result in improved survival in cancers such as renal cell carcinoma. Currently, the impact primary tumor resection has on survival in stage IV colon cancer patients is unknown. Methods: The SEER dataset was queried for patients who presented with histologically confirmed, stage IV colon cancer from 1998-2011. We excluded patients with rectal cancer, multiple primary tumors, age <18 or >90 years, diagnosis upon autopsy/death record, mortality within 30 days of diagnosis, or resection of other tumor sites (regional or distant). Cox proportional hazard models were used to assess demographic and clinical factors predictive of disease specific and overall survival. To limit group differences, a 1:1 matched analysis was also performed on patients who underwent primary resection compared to patients who did not. Results: A total of 28,068 stage IV colon cancer patients were evaluated, of which 70.3% underwent resection. Among the variables studied, multivariate models showed that patients who underwent primary tumor resection were at lower risk of disease-specific and overall mortality, with hazard ratios (HR) of 0.44 (0.43-0.46) and 0.45 (0.43-0.47), respectively. In the matched analysis (n=5,410 in each group), patients who underwent resection of the primary tumor remained at decreased risk of disease-specific and overall mortality, HR 0.48 (0.45-0.52) and 0.49 (0.46-0.53), respectively. The median survival and 3-year survival after matching was 17 and 9 months and 23% and 6% in the resection and nonresection groups, respectively, p<0.0001. Conclusions: The majority (70.3%) of patients in the United States with stage IV colon cancer undergo resection of primary tumors. Analyses of SEER data suggests that resection of the primary tumor may result in improved DSS and OS in patients with stage IV colon cancer. A prospective, randomized trial is warranted to confirm a survival benefit.