Background: The impact of sidedness in the high-risk stage II colorectal cancer (CRC) setting is uncertain. Although controversial, available data suggest a possible modest benefit of adjuvant chemotherapy (CT) in the adjuvant scenario. The aim of this study is to analyze the overall survival (OS) and recurrence-free survival (RFS) according to the tumor side.
Patients and methods: In this single-center retrospective cohort, we analyzed patients treated between January 2011 and December 2018. We evaluated OS and RFS of high-risk patients according to the tumor side and considering adjuvant CT exposure and clinical and molecular features.
Results: A total of 1047 patients with stage II CRC were evaluated. Of these, 540 had high-risk criteria and microsatellite stability (MSS) or unknown status. One hundred fifty-seven (29%) patients had right-sided tumors, and 352 (65.2%) had left-sided tumors. Most patients received adjuvant CT, and the majority of them had T3 stage tumors, ≥ 12 lymph node resection, left tumor, MSS, and moderate differentiation. OS did not differ according to tumor side (5-year OS rates: 81.9% for right-sided tumors vs. 83% for left-sided tumors; hazard ratio, 0.91; 95% confidence interval, 0.55-1.53; P = .744). Adjuvant CT was associated with a superior RFS and OS, with 5-year OS rates of 87.7% versus 76.1% in the no-adjuvant group (hazard ratio, 0.46; 95% CI, 0.28-0.73; P = .001).
Conclusion: The tumor side did not influence the outcomes in this study. Adjuvant CT was associated with improved RFS and OS in patients with high-risk stage II CRC, with a total gain of 11.6% in 5-year OS.
Keywords: Adjuvant therapy; Colorectal cancer; Early stage; Gastrointestinal cancer; Sidedness.
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