INTRODUCTION Metformin may be associated with reduced colorectal cancer (CRC) risk, but findings from previous studies have been inconsistent and had insufficient sample sizes to examine whether the association differs by anatomic site. This study examined whether metformin was associated with reduced CRC risk, both overall and stratified by anatomic site, in a large sample of persons with diabetes who underwent colonoscopy. METHODS We performed a case-control study of US Veterans with prevalent diabetes who underwent colonoscopy between 1999 and 2014 using Department of Veterans Affairs electronic health record data. Cases were defined by presence of CRC at colonoscopy, while controls had normal colonoscopy. The primary exposure was metformin use at time of colonoscopy (yes/no). Association of metformin exposure with CRC (further stratified by proximal, distal, or rectal subsite) was examined using multivariable and multinomial logistic regression and summarized by odds ratios (ORs) with 95% confidence intervals (CIs). RESULTS We included 6,650 CRC patients and 454,507 normal colonoscopy patients. CRC cases were older and had lower metformin exposure. Metformin was associated with 8% relative reduction in CRC odds (OR: 0.92, 95% CI: 0.87-0.96). By subsite, metformin was associated with a 14% statistically significant reduced rectal cancer odds (OR: 0.86, 95% CI: 0.78-0.94) but no reduced distal or proximal cancer odds. DISCUSSION Metformin was associated with reduced CRC odds-particularly rectal cancer-in a large sample of persons with diabetes undergoing colonoscopy.

中文翻译：

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二甲双胍可降低糖尿病患者患结直肠癌的几率。


简介 二甲双胍可能与降低结直肠癌 (CRC) 风险相关，但之前的研究结果不一致，并且样本量不足，无法检验这种关联是否因解剖部位而异。这项研究在接受结肠镜检查的糖尿病患者的大样本中检验了二甲双胍是否与总体和按解剖部位分层的结直肠癌风险降低相关。方法 我们利用退伍军人事务部电子健康记录数据，对 1999 年至 2014 年间接受结肠镜检查的患有糖尿病的美国退伍军人进行了一项病例对照研究。病例的定义是结肠镜检查时存在结直肠癌，而对照组的结肠镜检查结果正常。主要暴露是结肠镜检查时使用二甲双胍（是/否）。使用多变量和多项逻辑回归检查二甲双胍暴露与 CRC 的关联（进一步按近端、远端或直肠亚位点分层），并通过比值比 (OR) 和 95% 置信区间 (CI) 进行总结。结果 我们纳入了 6,650 名 CRC 患者和 454,507 名正常结肠镜检查患者。结直肠癌病例年龄较大，二甲双胍暴露量较低。二甲双胍可使 CRC 发生率相对降低 8%（OR：0.92，95% CI：0.87-0.96）。按亚部位来看，二甲双胍可显着降低 14% 的直肠癌发生率（OR：0.86，95% CI：0.78-0.94），但并未降低远端或近端癌症发生率。讨论 在接受结肠镜检查的糖尿病患者的大样本中，二甲双胍可降低结直肠癌（尤其是直肠癌）的发病率。