Timing of primary tumor resection after systemic chemotherapy initiation among patients with metastatic colon cancer.

Abstract

65 Background: In patients with resectable, metastatic colon cancer, the optimal timing of definitive resection of the primary tumor after initiation of chemotherapy remains unclear. Our goal is to identify factors that influence the interval between chemotherapy and definitive surgical management, and its impact on overall survival. We hypothesize that patients with shorter chemotherapy-to-surgery intervals (less than 60 days or about 2 months) compared to 61-180 days (2-6 months) or greater than 180 days (> 6 months), will have the worst overall survival. Methods: We conducted a retrospective analysis of all patients diagnosed with metastatic colon cancer from 2004-2016 who underwent resection of both primary tumor and distant metastatic site from the National Cancer Database (NCDB). Among those who received chemotherapy prior to surgery, we calculated the interval days between initiation of chemotherapy and primary tumor resection. Descriptive analysis, logistic regression, and overall survival was performed comparing patients with chemotherapy-to-surgery intervals of <60, 60-180, and >180 days. Results: A total of 2,238 patients were included, of which 143 (6%), 1446 (65%), and 649 (29%) were in the <60, 60-180, and >180 days groups, respectively. Similar distribution of patients across groups was observed for age, gender, insurance status, income, education level, distance travel, and Charlson-Deyo scores. Poorly differentiated tumors were more frequent in the <60 days group (12% vs 2-9% for other grades, p=0.001) as well as presence of lymphovascular invasion (8% vs 4%, p = 0.006). The odds of receiving care at an academic facility were lower in the <60 days group (OR: 0.52, 95% CI 0.273-0.994). Overall survival was significantly reduced in the <60 days group compared to 60-180 days (HR= 0.562, 95% C: 0.38-0.82). Conclusions: In this retrospective study from a national database, shorter chemotherapy-to-surgery interval (<60 days) was associated with poorly differentiated tumors and lymphovascular invasion. The odds of receiving surgery in <60 days of receiving chemotherapy was lower in academic/research facilities. A reduction in overall survival was observed in the shorter interval (<60 days) group compared to longer intervals. More research is needed to define the optimal chemotherapy-surgery interval and factors that influence this.