关于饮食脂肪摄入量与乳腺癌女性死亡风险的观察研究结果互相矛盾，故有必要对干预研究结果进行分析。
2020年2月7日，美国临床肿瘤学会《临床肿瘤学杂志》在线发表洛杉矶加利福尼亚大学、弗雷德哈钦森癌症研究中心、哈佛大学、布莱根医院和波士顿妇女医院、亚利桑那大学、爱因斯坦医学院、石溪大学、田纳西大学、布法罗大学、爱荷华大学、印第安那大学、乔治城大学的女性健康倡议（WHI）饮食干预研究长期随访结果二次分析报告，探讨了低脂饮食对乳腺癌女性死亡风险的长期影响。
WHI: Women's Health Initiative (NCT00000611)
女性健康倡议（WHI）是全世界规模最大、随访时间最长的疾病预防研究之一，预算达6.25亿美元，始于1991年，共入组绝经后女性超过16万，包括3项随机对照临床干预研究的6万8132位女性和1项观察研究的9万3676位女性。
其中，来自全美国40个研究中心、入组时年龄50～79岁、无乳腺癌史、饮食脂肪摄入量占总能量≥32%的4万8835例绝经后女性，按3∶2的比例被随机分入两组：常规饮食对照组2万9294例、饮食干预组1万9541例。饮食干预目标为脂肪摄入量减少至占总能量的20%，同时增加蔬菜、水果和谷物的摄入量。通过集中复核医疗记录，确认随访期间新发生的乳腺癌。通过查询全国死亡登记数据库，计算死亡风险。
结果，经过中位8.5年，干预组与对照组相比：
乳腺癌发病风险相似：0.42%比0.45%（风险比：0.91，95%置信区间：0.83～1.01，P=0.09）
乳腺癌所致死亡风险相似：0.016%比0.024%（风险比：0.67，95%置信区间：0.43～1.06，P=0.08）
乳腺癌之后死亡风险显著较低：0.025%比0.038%（风险比：0.65，95%置信区间：0.45～0.94，P=0.02）
经过中位16.1年随访，干预组与对照组相比：
乳腺癌发病风险相似：0.44%比0.46%（风险比：0.97，95%置信区间：0.90～1.04，P=0.34）
乳腺癌所致死亡风险相似：0.035%比0.039%（风险比：0.91，95%置信区间：0.72～1.15，P=0.41）
乳腺癌之后死亡风险显著较低：0.085%比0.110%（风险比：0.82，95%置信区间：0.70～0.96，P=0.01）
现在，经过中位19.6年随访，干预组与对照组相比：
乳腺癌发病风险相似（风险比：0.95，95%置信区间：0.89～1.02）
乳腺癌之后死亡风险显著较低：0.12%比0.14%（风险比：0.85，95%置信区间：0.74～0.96，P=0.01）
乳腺癌所致死亡风险显著较低：0.037%比0.047%（风险比：0.79；95%置信区间：0.64～0.97，P=0.02）
因此，该大样本干预研究长期随访结果证实，低脂饮食同时增加蔬菜、水果和谷物的摄入量，可以减少绝经后女性乳腺癌相关死亡风险。
相关链接
J Clin Oncol. 2020 Feb 7. [Epub ahead of print]
Dietary Modification and Breast Cancer Mortality: Long-Term Follow-Up of the Women's Health Initiative Randomized Trial.
Chlebowski RT, Aragaki AK, Anderson GL, Pan K, Neuhouser ML, Manson JE, Thomson CA, Mossavar-Rahmani Y, Lane DS, Johnson KC, Wactawski-Wende J, Snetselaar L, Rohan TE, Luo J, Barac A, Prentice RL; Women's Health Initiative.
Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA; Fred Hutchinson Cancer Research Center, Seattle, WA; Brigham and Women's Hospital, Harvard Medical School, Boston, MA; University of Arizona, Tucson, AZ; Albert Einstein College of Medicine, Bronx, NY; Stony Brook University School of Medicine, Stony Brook, NY; University of Tennessee, Memphis, TN; University at Buffalo, Buffalo, NY; University of Iowa, Iowa City, IA; Indiana University, Bloomington, IN; Georgetown University, Washington, DC.
PURPOSE: Observational studies of dietary fat intake and breast cancer have reported inconsistent findings. This topic was addressed in additional analyses of the Women's Health Initiative (WHI) Dietary Modification (DM) clinical trial that evaluated a low-fat dietary pattern influence on breast cancer incidence.
METHODS: In the WHI DM trial, 48,835 postmenopausal women, ages 50-79 years, with no prior breast cancer, and a dietary fat intake of ≥ 32% of energy were randomly assigned at 40 US centers to a usual diet comparison group (60%) or dietary intervention group (40%). The goals were to reduce fat intake to 20% of energy and increase vegetable, fruit, and grain intake. Breast cancers were confirmed after central medical record review and serial National Death Index linkages to enhance mortality findings.
RESULTS: During 8.5 years of dietary intervention, breast cancer incidence and deaths as a result of breast cancer were nonsignificantly lower in the intervention group, while deaths after breast cancer were statistically significantly lower both during intervention and through a 16.1-year (median) follow-up. Now, after a long-term, cumulative 19.6-year (median) follow-up, the significant reduction in deaths after breast cancer persists (359 [0.12%] v 652 [0.14%] deaths; hazard ratio [HR], 0.85; 95% CI, 0.74 to 0.96; P = .01), and a statistically significant reduction in deaths as a result of breast cancer (breast cancer followed by death attributed to the breast cancer) emerged (132 [0.037%, annualized risk] v 251 [0.047%] deaths, respectively; HR, 0.79; 95% CI, 0.64 to 0.97; P = .02).
CONCLUSION: Adoption of a low-fat dietary pattern associated with increased vegetable, fruit, and grain intake, demonstrably achievable by many, may reduce the risk of death as a result of breast cancer in postmenopausal women.
PMID: 32031879
DOI: 10.1200/JCO.19.00435
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