Weight gain during adjuvant endocrine treatment for early-stage breast cancer: What is the evidence?

Most breast cancer (BC) tumors are early stage and hormone receptor positive, where treatment generally includes adjuvant endocrine treatment (ET). Oncology providers and women about to start ET want to know about side effects, including potential weight gain. The aim of this study was a literature review to identify the independent effect of ET on post-diagnosis weight gain. Weight gain is of concern with regard to potential associations with BC recurrence, mortality, and quality of life in survivorship. We conducted a targeted review of the literature. Thirty-eight studies met our inclusion criteria. Patient-reported weight gain ranged widely from 18 to 52 % of patients in Year 1 and from 7 to 55 % in Year 5. Some studies reported categories of weight change: lost weight (9-17 %), stable weight (47-64 %), and gained weight (27-36 %). Most studies comparing ET with placebo or tamoxifen with AI reported no significant difference between the two groups. Wide-ranging and inconsistent results point to the need for further research to clarify annual weight change (loss, gain, stability) from BC diagnosis through 5 years of ET and beyond. There is also a need to explore weight change by type of ET and to explore risk factors for weight gain in women on ET, including tumor type, sociodemographic characteristics, and health behaviors. More specific information is needed to identify high-risk BC patients who could be targeted for weight management interventions.