Weight Gain After Breast Cancer Diagnosis and All-Cause Mortality: Systematic Review and Meta-Analysis

Background: Overweight and obesity are associated with breast cancer mortality. However, the relationship between postdiagnosis weight gain and mortality is unclear. We conducted a systematic review and meta-analysis of weight gain after breast cancer diagnosis and breast cancer-specific, all-cause mortality and recurrence outcomes. Methods: Electronic databases identified articles upthrough December 2014, including: PubMed (1966-present), EMBASE (1974-present), CINAHL (1982-present), and Web of Science. Language and publication status were unrestricted. Cohort studies and clinical trials measuring weight change after diagnosis and all-cause/breast cancer-specific mortality or recurrence were considered. Participants were women age 18 years or older with stage I-IIIC breast cancer. Fixed effects analysis summarized the association between weight gain (>= 5.0% body weight) and all-cause mortality; all tests were two-sided. Results: Twelve studies (n = 23 832) were included. Weight gain (>= 5.0%) compared with maintenance (<+/- 5.0%) was associated with increased all-cause mortality (hazard ratio [HR] = 1.12, 95% confidence interval [CI] = 1.03 to 1.22, p=.01, I-2 = 55.0%). Higher risk of mortality was apparent for weight gain >= 10.0% (HR = 1.23, 95% CI = 1.09 to 1.39, p<.001); 5% to 10.0% weight gain was not associated with all-cause mortality (p=.40). The association was not statistically significant for those with a prediagnosis body mass index (BMI) of less than 25 kg/m(2) (HR = 1.14, 95% CI = 0.99 to 1.31, p=.07) or with a BMI of 25 kg/m(2) or higher (HR = 1.00, 95% CI = 0.86 to 1.16, p=.19). Weight gain of 10.0% or more was not associated with hazard of breast cancer-specific mortality (HR = 1.17, 95% CI = 1.00 to 1.38, p=.05). Conclusions: Weight gain after diagnosis of breast cancer is associated with higher all-cause mortality rates compared with maintaining body weight. Adverse effects are greater for weight gains of 10.0% or higher.