Supplementary Material for: Incidence and mortality of post-polypectomy colorectal cancer in patients with low-risk adenomas: A systematic review and meta-analysis of observational studies

Introduction: The long-term risks of post-polypectomy colorectal cancer (CRC) incidence and mortality among patients with low-risk adenomas (LRAs) are unclear. This study aimed to perform a systematic review and meta-analysis of the risk of CRC incidence and mortality following LRAs removal. Methods: We searched the PubMed, Embase, and Cochrane library for studies that reported the risk of metachronous CRC incidence and mortality after colonoscopy. The primary outcome was the risk of CRC incidence and mortality in patients with LRAs. Random-effects models were used to calculate pooled risk ratio (RR) with 95% CI. Results: Thirteen observational studies with 1,750,305 patients (45.4% male; follow-up: 4.5-16.5 years) were included. A meta-analysis of seven studies showed a higher CRC incidence in patients with LRAs than those without adenomas [per 10,000 person-years: 5.2 vs 3.9; RR 1.25 (95% CI 1.05-1.49), I2=0%]. However, the CRC-related death was not significantly different between the two groups [RR 1.13 (95% CI 0.75-1.69), I2=0%]. When compared with the general population, the meta-analysis showed a significantly lower risk of CRC incidence in patients with LRAs [RR 0.59 (95%CI 0.45-0.77), I2=0%], and another three studies, which could not be pooled, showed a reduction in the risk of CRC-related death in the LRAs group. Conclusions: Patients with LRAs have a small but higher risk of post-polypectomy CRC incidence than patients without adenomas. The marginally higher absolute incidence seemed insufficient for more intensive surveillance colonoscopy, but the significant difference suggested different follow-up strategies between patients with LRAs and those without adenomas.

引言：低风险腺瘤（low-risk adenomas, LRAs）患者行息肉切除术后，结直肠癌（colorectal cancer, CRC）的长期发病与死亡风险目前尚未明确。本研究旨在针对低风险腺瘤切除术后结直肠癌发病与死亡风险开展系统综述与荟萃分析。
方法：我们在PubMed、Embase及Cochrane图书馆中检索了报道结肠镜检查后异时性结直肠癌发病与死亡风险的相关研究。本研究的主要结局为低风险腺瘤患者的结直肠癌发病与死亡风险。我们采用随机效应模型计算合并风险比（risk ratio, RR）及95%置信区间（95% CI）。
结果：本研究共纳入13项观察性研究，涉及1750305例患者（男性占比45.4%；随访时长4.5~16.5年）。针对7项研究的荟萃分析结果显示，低风险腺瘤患者的结直肠癌发病率高于无腺瘤患者[每10000人年：5.2 vs 3.9；RR=1.25（95%CI：1.05~1.49），I²=0%]。然而，两组患者的结直肠癌相关死亡率无显著差异[RR=1.13（95%CI：0.75~1.69），I²=0%]。与普通人群相比，荟萃分析结果显示低风险腺瘤患者的结直肠癌发病风险显著更低[RR=0.59（95%CI：0.45~0.77），I²=0%]；另有3项无法合并分析的研究显示，低风险腺瘤组患者的结直肠癌相关死亡风险有所降低。
结论：与无腺瘤患者相比，低风险腺瘤患者息肉切除术后的结直肠癌发病风险仅小幅升高。该绝对发病率的轻微升高似乎不足以支持开展更强化的结肠镜监测，但两者间的显著差异提示，低风险腺瘤患者与无腺瘤患者应采用不同的随访策略。