Background: Most randomized controlled trials (RCTs) assessing the impact of diet on cancer have been short term (<1 year), mostly evaluating breast cancer survivors. Given the many-year interval that is generally required for an intervention to have an impact on cancer risk or prognosis, as well as the fact that lifestyle strategies such as diet modification frequently fail due to lack of adherence over the long term, we focused this systematic review only on longer-term (≥1 year) intervention reports. Diet intervention reports focused on reducing cancer risk in overweight and obese individuals target caloric restriction (every day, some days, or most hours of each day). Methods: This study is a systematic review of RCTs lasting at least 1 year, testing dietary interventions with a primary or secondary endpoint of cancer or a biomarker linked to cancer. Results: Fifty-one reports met our review criteria. Twenty of fifty-one (39%) reports are RCTs where the primary endpoint was cancer or a cancer-related biomarker, while the other reports evaluated reports where cancer or a cancer-related biomarker was a secondary endpoint. Thirteen of twenty (65%) primary reports evaluated isocaloric, and the remaining eight evaluated low-calorie diets. All but one of the primary and two secondary isocaloric diet reports evaluated the benefit of a low-fat diet (LFD), with the other three evaluating a Mediterranean diet (MedD). More LCD vs. isocaloric diet primary reports (71% vs. 38%) demonstrated cancer or cancer-related biomarker benefit; the difference in chance of benefit with secondary reports was 85% for LCD vs. 73% for isocaloric diets. Three of three MedD reports demonstrated benefit. Sixty-nine percent (20/29) of the secondary reports came from two large reports: the WHI diet modification trial (15 secondary reports) and the polyp prevention trial (5 secondary reports). Nineteen of twenty-two (86%) primary reports enrolled only women, and three enrolled both men and women. No study that met our criteria enrolled only men, comprising 1447 men in total vs. 62,054 women. Fifteen of twenty (75%) primary reports focus on healthy women or women with breast cancer. Adherence findings are discussed when provided. Conclusions: More long-term RCTs evaluating cancer and cancer-related biomarker endpoints are needed, especially for cancers at sites other than the breast.
背景：大多数评估饮食对癌症影响的随机对照试验（RCT）均为短期研究（<1年），且主要针对乳腺癌幸存者。鉴于干预措施通常需要多年时间才能对癌症风险或预后产生影响，以及饮食调整等生活方式策略常因长期依从性不足而失败，本系统综述仅关注长期（≥1年）干预研究报告。针对超重和肥胖人群的饮食干预报告主要聚焦于热量限制（每日、部分天数或每日大部分时间）。方法：本研究系统综述了持续时间至少1年的随机对照试验，这些试验以癌症或与癌症相关的生物标志物作为主要或次要终点，测试饮食干预效果。结果：51篇报告符合综述标准。其中20篇（39%）报告是以癌症或癌症相关生物标志物为主要终点的随机对照试验，其余报告则评估了以癌症或癌症相关生物标志物为次要终点的研究。在20篇主要报告中，13篇（65%）评估了等热量饮食，其余8篇评估了低热量饮食。除一篇主要报告和两篇次要等热量饮食报告外，所有报告均评估了低脂饮食的益处，另外三篇报告评估了地中海饮食。与等热量饮食相比，更多低热量饮食的主要报告（71% vs. 38%）显示出癌症或癌症相关生物标志物的益处；次要报告中，低热量饮食与等热量饮食的获益概率差异分别为85%和73%。三篇地中海饮食报告均显示出益处。69%（20/29）的次要报告来自两项大型研究：WHI饮食调整试验（15篇次要报告）和息肉预防试验（5篇次要报告）。22篇主要报告中，19篇（86%）仅纳入女性参与者，3篇同时纳入男性和女性。符合标准的报告中无仅纳入男性的研究，男性参与者总计1447人，女性为62,054人。20篇主要报告中，15篇（75%）聚焦于健康女性或乳腺癌患者。报告提供的依从性结果已进行讨论。结论：需要更多评估癌症及癌症相关生物标志物终点的长期随机对照试验，尤其是针对乳腺癌以外其他部位的癌症研究。
肿瘤(癌症)患者之家