Background The history of gestational diabetes mellitus (GDM) has been associated with breast cancer risk in some studies, particularly in young women, but results of cohort studies are conflicting. Methods We pooled data from 257 290 young (age <55 years) women from five cohorts. We used multivariable Cox proportional-hazards regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between GDM history and risk of breast cancer, overall and by oestrogen receptor (ER) status, before age 55 years, adjusted for established breast cancer risk factors. Results Five percent of women reported a history of GDM and 6842 women reported an incident breast-cancer diagnosis (median follow-up = 16 years; maximum = 24 years). Compared with parous women without GDM, women with a history of GDM were not at increased risk of young-onset breast cancer overall (HR = 0.90; 95% CI: 0.78, 1.03) or by ER status (HR = 0.96; 95% CI: 0.79, 1.16 for ER-positive; HR = 1.07; 95% CI: 0.78, 1.47 for ER-negative). Compared with nulliparous women, parous women with a history of GDM had a lower risk of breast cancer overall (HR = 0.79; 95% CI: 0.68, 0.91) and of ER-positive (HR = 0.82; 95% CI: 0.66, 1.02) but not ER-negative (HR = 1.09; 95% CI: 0.76, 1.54) invasive breast cancer. These results were consistent with the HRs comparing parous women without GDM to nulliparous women. Conclusions Results of this analysis do not support the hypothesis that GDM is a risk factor for breast cancer in young women. Our findings suggest that the well-established protective effect of parity on risk of ER-positive breast cancer persists even for pregnancies complicated by GDM.

中文翻译：

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妊娠期糖尿病与 55 岁之前患乳腺癌的风险


背景 在一些研究中，妊娠糖尿病（GDM）史与乳腺癌风险相关，特别是在年轻女性中，但队列研究的结果是相互矛盾的。方法 我们汇集了来自 5 个队列的 257 290 名年轻女性（年龄 <55 岁）的数据。我们使用多变量 Cox 比例风险回归来估计 55 岁之前 GDM 病史与乳腺癌风险之间关联的风险比 (HR) 和 95% 置信区间 (CI)，总体以及雌激素受体 (ER) 状态。根据已确定的乳腺癌危险因素进行调整。结果 5% 的女性报告有 GDM 病史，6842 名女性报告了乳腺癌诊断（中位随访 = 16 年；最长 = 24 年）。与没有 GDM 的经产妇女相比，有 GDM 病史的妇女患早发乳腺癌的总体风险并未增加（HR = 0.90；95% CI：0.78，1.03），或根据 ER 状态（HR = 0.96；95% CI） ：ER 阳性为 0.79，1.16；HR = 1.07；95% CI：ER 阴性为 0.78，1.47。与未生育过的女性相比，有 GDM 病史的已产女性总体上患乳腺癌的风险较低 (HR = 0.79; 95% CI: 0.68, 0.91) 和 ER 阳性风险较低 (HR = 0.82; 95% CI: 0.66, 1.02) ）但不是 ER 阴性（HR = 1.09；95% CI：0.76，1.54）浸润性乳腺癌。这些结果与比较没有 GDM 的经产妇女与未生育妇女的 HR 一致。结论 该分析结果不支持 GDM 是年轻女性乳腺癌危险因素的假设。我们的研究结果表明，即使对于并发 GDM 的妊娠，生育对 ER 阳性乳腺癌风险的既定保护作用仍然存在。