Current treatment strategies and patterns of recurrence in locally advanced colon cancer.

Abstract

e15171 Background: Locally advanced colon cancer (LACC) is a frequent presentation and has a high rate of recurrence. The aim of this study was to evaluate current population-based strategies in LACC patients, and to analyze patterns of recurrence. Methods: We conducted a retrospective review of all patients treated at a regional cancer agency with a diagnosis of LACC between 2005 and 2015 treated with curative intent resection. Inclusion criteria were adults with T4 colon cancer, 16 cm above the anal verge, with no evidence of distant metastases. Descriptive statistics were used to define the study population. Kaplan-Meier and Cox-proportional hazards modeling were used for survival analysis. Results: 1394 patients with LACC were reviewed. Median age was 69 [IQR 60-77] and 49.3% were female. Primary tumor location was right-sided in 57.1% of cases. Most tumors were T4a (69.4%) and 39.4% were node positive. A total of 35.4% had urgent/emergent surgery, 46.4% were at least partially obstructed, 22.0% were perforated and 1.9% had a diverting ostomy as an initial operation. En-bloc multi-visceral resection occurred in 23.5% of cases. Positive margins were present in 14.3%. Only 1.6% had neoadjuvant chemotherapy and 0.8% had neoadjuvant chemoradiation. Adjuvant chemotherapy was delivered in 59.8% and adjuvant chemoradiation in 2.8%. Median follow up was 37 months. During follow up 681 (48.9%) patients died and 584 (41.9%) patients developed recurrence. In the entire cohort, rates of recurrences were local-regional (14.7%) and distant metastatic (35.1%). Overall survival for the entire cohort was 63 months [95% CI 55.7-70.3] and recurrence-free survival was 61 months [95% CI 38.8-83.2]. Multivariate analysis identified age (HR 1.03, 95% CI [1.02-1.05] p < 0.001), node negative status (HR 0.62, 95% CI [0.45-0.84] p = 0.002) and positive margin (HR 1.79, 95% CI [1.24-2.57] p = 0.002) as predictive of overall survival after adjusting for confounding factors. Predictive factors for recurrence-free survival were node negative status (HR 0.55, 95% CI [0.39-0.77] p < 0.001) and positive margin (HR 1.51, 95% CI [1.02-2.23] p = 0.038). Conclusions: Recurrence after curative intent treatment for LACC is common. Recurrence and survival patterns are significantly influenced by tumor nodal status and margin positivity.