근치적 수술을 시행받은 2, 3기 직장암 환자에서 현미부수체 불안정성의 예후인자로서의 역할

Abstract

Background: Microsatellite instability (MSI) is one of the most important prognostic factors in patients with a resected colon cancer but its impact in rectal cancer cases has not been fully evaluated. We investigated whether the MSI status affects the survival outcomes in stage II and III rectal cancer patients who have undergone an upfront curative resection. Methods: A total of 1,103 patients who were treated between February 2008 and August 2015 at Asan Medical Center were included in this study. The major eligibility criteria included primary adenocarcinoma of the rectum, upfront surgery of curative intent, pathologic stage II/III disease, and available polymerase chain reaction (PCR)-based MSI results. The study endpoints were disease-free survival (DFS) and overall survival (OS). Results: Twenty-four patients (2.2%) in the total cohort were found to be MSI-high (MSI-H). MSI-H patients were significantly associated with histologically poorly differentiated tumors (P=0.001) and with a family history of colorectal cancers (P=0.008). The 5-year DFS and OS for the whole cohort was 70.1% (95% confidence interval [CI] 67.4 – 72.8) and 83.1% (95% CI 80.9 – 85.3), respectively. In univariate analysis, a high pathologic stage, poorly differentiated tumor, mid to distal located tumor (anal verge < 8 cm), positive resection margin, presence of lymphovascular or perineural invasion and high preoperative level of carcinoembryonic antigen (> 6.0 ng/mL) were significantly associated with a shorter DFS and OS. However, neither DFS nor OS were statistically significantly different according to the MSI status. The 5-year DFS rate was 78.0% in MSI-H patients and 69.9% in MSI-low (MSI-L) or microsatellite stable (MSS) patients (Hazard ratio [HR] 0.84, 95% CI 0.35 – 2.02; P=0.689). The 5-year OS rates for MSI-H and MSI-L/MSS patients were 84.0% and 83.1%, respectively (HR 0.86, 95% CI 0.27 – 2.69; P=0.790). By multivariate analysis, the MSI status did not affect either the DFS (HR 1.00, 95% CI 0.40 – 2.47; P=0.994) or OS (HR 0.85, 95% CI 0.26 – 2.73; P=0.778). Conclusion: MSI-H tumors are rarely observed in rectal adenocarcinoma and the MSI status may not affect the survival outcome in patients with a resected rectal cancer.