低脂肪飲食模式與乳腺癌總生存的相關性：隨機臨床研究的二次分析

編者按：根據美國的女性健康倡議隨機臨床研究結果，低脂飲食模式與乳腺癌死亡風險較低相關。不過，飲食對乳腺癌診斷後的生存影響程度如何？實施低脂飲食模式是否與乳腺癌的結局相關？

2018年5月24日，《美國醫學會雜誌》腫瘤學分冊在線發表希望之城國家醫學中心、弗雷德·哈欽森癌症研究中心、韋恩州立大學、哈佛大學醫學院、布列根和波士頓婦女醫院、洛杉磯加利福尼亞大學、斯坦福大學、紐約愛因斯坦醫學院、紐約石溪大學、戴維斯加利福尼亞大學、愛荷華大學的女性健康倡議隨機臨床研究二次分析報告，比較了低脂飲食模式與常規飲食對乳腺癌女性總生存（乳腺癌診斷至任何原因所致死亡的生存）之間的相關性。結果發現，飲食乾預期間1764位絕經後女性被診斷為乳腺癌，隨機分配接受低脂飲食模式患者的乳腺癌總生存改善。因此，改變飲食可能影響乳腺癌的結局。

女性健康倡議隨機臨床研究於19931998年在40個美國臨床中心進行，參與者為4萬8835位絕經後女性，既往無乳腺癌，根據食物頻率問卷，飲食脂肪攝入量超過總能量的32%。1萬9541位參與者（40%）被隨機分配至飲食乾預組，目標為脂肪攝入量減少至總能量的20%，增加水果、蔬菜、穀物的攝入量；2萬9294位參與者（60%）被隨機分配至常規飲食對照組。發生乳腺癌的飲食乾預組參與者繼續參與後續飲食乾預活動。主要結局衡量指標為飲食乾預期間（中位8.5年）被診斷為乳腺癌後的乳腺癌總生存，診斷後隨訪結束時（中位11.5年）進行事後分析。

結果發現，飲食乾預期間，1764位女性被診斷為乳腺癌，篩查時、診斷時平均年齡分別為62.7±6.7歲、67.6±6.9歲。

死亡共516例，飲食乾預組與飲食對照組的女性相比：

乳腺癌總生存率較高（10年生存率：82%比78%，死亡風險比：0.78，95%置信區間：0.650.94，P=0.01）

乳腺癌所致死亡較少（68例比120例，死亡風險比：0.86，95%置信區間：0.641.17）

其他癌所致死亡較少（36例比65例，死亡風險比：0.76，95%置信區間：0.501.17）

心血管所致死亡較少（27例比64例，死亡風險比：0.62，95%置信區間：0.390.99）

因此，對於飲食乾預期間被診斷為乳腺癌的女性，飲食乾預組患者的總生存率較高，主要由於乳腺癌、其他癌、心血管所致死亡較少。

JAMA Oncol. 2018 May 24. [Epub ahead of print]

Association of Low-Fat Dietary Pattern With Breast Cancer Overall Survival: A Secondary Analysis of the Women"s Health Initiative Randomized Clinical Trial.

Rowan T. Chlebowski; Aaron K. Aragaki; Garnet L. Anderson; Michael S. Simon; JoAnn E. Manson; Marian L. Neuhouser; Kathy Pan; Marcia L. Stefanic; Thomas E. Rohan; Dorothy Lane; Lihong Qi; Linda Snetselaar; Ross L. Prentice.

City of Hope National Medical Center, Duarte, California; Fred Hutchinson Cancer Research Center, Seattle, Washington; Wayne State University, Detroit, Michigan; Brigham and Women"s Hospital, Harvard Medical School, Boston, Massachusetts; UCLA Medical Center, Torrance, California; Stanford University, Palo Alto, California; Albert Einstein College of Medicine, Bronx, New York; Stony Brook University, Stony Brook, New York; University of California at Davis; University of Iowa, Iowa City/Davenport.

This secondary analysis of the Women"s Health Initiative randomized clinical trial investigates the association of a low-fat dietary pattern vs a usual diet comparison with overall survival among women with breast cancer.

QUESTION: Is implementation of a low-fat eating pattern associated with breast cancer outcome?

FINDING: In this secondary analysis of the Women"s Health Initiative randomized clinical trial that included 1764 postmenopausal women who received a diagnosis of breast cancer during the dietary intervention period, those randomized to a low-fat dietary pattern had increased breast cancer overall survival.

MEANING: A dietary change may be able to influence breast cancer outcome.

IMPORTANCE: In a randomized clinical trial, a low-fat eating pattern was associated with lower risk of death after breast cancer. However, the extent to which results were driven by dietary influence on survival after breast cancer diagnosis was unknown.

OBJECTIVE: To determine the association of a low-fat dietary pattern with breast cancer overall survival (breast cancer followed by death from any cause measured from cancer diagnosis).

DESIGN, SETTING, AND PARTICIPANTS: This is a secondary analysis of the Women"s Health Initiative randomized clinical trial that was conducted at 40 US clinical centers enrolling participants from 1993 through 1998. Participants were 48835 postmenopausal women with no previous breast cancer and dietary fat intake of greater than 32% by food frequency questionnaire.

INTERVENTIONS: Participants were randomized to a dietary intervention group (40%; n=19541) with goals to reduce fat intake to 20% of energy and increase fruit, vegetable, and grain intake or a usual-diet comparison group (60%; n=29294). Dietary group participants with incident breast cancers continued to participate in subsequent dietary intervention activities.

MAIN OUTCOMES AND MEASURES: Breast cancer overall survival for incident breast cancers diagnosed during the 8.5-year (median) dietary intervention, examined in post hoc analyses after 11.5 years (median) postdiagnosis follow-up.

RESULTS: Of 1764 women diagnosed with breast cancer during the dietary intervention period, mean (SD) age at screening was 62.7 (6.7) years and age at diagnosis was 67.6 (6.9) years. With 516 total deaths, breast cancer overall survival was significantly greater for women in the dietary intervention group than in the usual-diet comparison group (10-year survival of 82% and 78%, respectively; hazard ratio [HR], 0.78; 95% CI, 0.65-0.94; P=.01). In the dietary group there were fewer deaths from breast cancer (68 vs 120; HR, 0.86; 95% CI, 0.64-1.17), other cancers (36 vs 65; HR, 0.76; 95% CI, 0.50-1.17), and cardiovascular disease (27 vs 64; HR, 0.62; 95% CI, 0.39-0.99).

CONCLUSIONS AND RELEVANCE: In women who received a diagnosis of breast cancer during the dietary intervention period, those in the dietary group had increased overall survival. The increase is due, in part, to better survival from several causes of death.