Background: Results of observational studies of the association between dietary fat and risk of invasive breast cancer have been inconsistent. In the Women's Health Initiative dietary modification (DM) randomized trial designed to lower fat intake, the intervention was not associated with a statistically significant reduction of overall breast cancer risk. However, the DM association with risk of ductal carcinoma in situ (DCIS) of the breast, a putative breast cancer precursor, has not been reported. Methods: A total of 48,835 postmenopausal women, ages 50–79 years at enrollment, with no breast cancer history and ≥32% of total energy intake from fat, were randomly assigned either to a dietary intervention ( n = 19,541) designed to reduce total fat intake to 20% of energy and to increase vegetable, fruit, and grain consumption, or to a comparison group ( n = 29,294). Cox proportional hazards models were used to estimate HRs and 95% confidence intervals for the association between the intervention and DCIS risk. Results: During 18.7 years (median) cumulative follow-up, including intervention (∼8.7 years) and post-intervention phases (∼13.0 years), 817 DCIS cases were ascertained. No evidence of an association between the DM intervention and DCIS risk was observed overall, or by trial phase (intervention and post-intervention). Similarly, no associations were found in subgroups defined by potential risk factors for DCIS. Conclusions: DM aiming to reduce fat intake was not associated with altered risk of DCIS. Impact: These results do not provide evidence of an association between dietary fat reduction and the risk of DCIS among postmenopausal women.

中文翻译：

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妇女健康倡议饮食调整试验中的低脂饮食调整和乳腺原位导管癌的风险

背景：关于膳食脂肪与浸润性乳腺癌风险之间关系的观察性研究结果不一致。在旨在降低脂肪摄入的女性健康倡议饮食调整 (DM) 随机试验中，干预与总体乳腺癌风险的统计学显着降低无关。然而，尚未报道 DM 与乳腺导管原位癌 (DCIS)（一种假定的乳腺癌前体）风险的相关性。方法：共有 48,835 名绝经后妇女，年龄在 50-79 岁之间，没有乳腺癌病史，脂肪总能量摄入量 ≥32%，被随机分配到旨在减少总能量摄入的饮食干预 (n = 19,541)脂肪摄入量达到能量的 20%，并增加蔬菜、水果和谷物的摄入量，或对照组（n = 29,294）。Cox 比例风险模型用于估计干预与 DCIS 风险之间关联的 HR 和 95% 置信区间。结果：在 18.7 年（中位）累积随访期间，包括干预（~8.7 年）和干预后阶段（~13.0 年），确定了 817 例 DCIS 病例。总体上或按试验阶段（干预和干预后）未观察到 DM 干预与 DCIS 风险之间存在关联的证据。同样，在由 DCIS 的潜在危险因素定义的亚组中也没有发现相关性。结论：旨在减少脂肪摄入的 DM 与 DCIS 风险的改变无关。影响：这些结果并未提供证据表明饮食脂肪减少与绝经后女性患 DCIS 的风险之间存在关联。Cox 比例风险模型用于估计干预与 DCIS 风险之间关联的 HR 和 95% 置信区间。结果：在 18.7 年（中位）累积随访期间，包括干预（~8.7 年）和干预后阶段（~13.0 年），确定了 817 例 DCIS 病例。总体上或按试验阶段（干预和干预后）未观察到 DM 干预与 DCIS 风险之间存在关联的证据。同样，在由 DCIS 的潜在危险因素定义的亚组中也没有发现相关性。结论：旨在减少脂肪摄入的 DM 与 DCIS 风险的改变无关。影响：这些结果并未提供证据表明饮食脂肪减少与绝经后女性患 DCIS 的风险之间存在关联。Cox 比例风险模型用于估计干预与 DCIS 风险之间关联的 HR 和 95% 置信区间。结果：在 18.7 年（中位）累积随访期间，包括干预（~8.7 年）和干预后阶段（~13.0 年），确定了 817 例 DCIS 病例。总体上或按试验阶段（干预和干预后）未观察到 DM 干预与 DCIS 风险之间存在关联的证据。同样，在由 DCIS 的潜在危险因素定义的亚组中也没有发现相关性。结论：旨在减少脂肪摄入的 DM 与 DCIS 风险的改变无关。影响：这些结果并未提供证据表明饮食脂肪减少与绝经后女性患 DCIS 的风险之间存在关联。