Body size and breast cancer prognosis in relation to hormone receptor and menopausal status: a meta-analysis

Obesity is associated with poor survival after breast cancer diagnosis in individual studies and meta-analyses. Evidence regarding associations of obesity with breast cancer-specific survival (BCSS) and overall survival (OS) in relation to hormone receptor status, or BCSS in relation to menopausal status has not been evaluated in a previous meta-analysis. In this study, we conducted a meta-analysis of the association of obesity with OS and BCSS in relation to hormone receptor status and menopausal status. MEDLINE, EMBASE, and COCHRANE databases from the first record to December 2011 and presentations made at major international meetings in the last 5 years were searched. We included observational or interventional studies reporting hazard ratios (HRs) of obesity with OS and/or BCSS in relation to hormone receptor and/or menopausal status. Twenty-one studies qualified, meeting the above criteria. The pooled HR for OS in heavier versus lighter women was 1.31 (95 % CI 1.17-1.46) for estrogen receptor/progesterone receptor (ER/PgR) positive cancers; 1.18 (95 % CI 1.06-1.31) for ER/PgR negative cancers; and the difference between the two groups was not significant (p = 0.31). The pooled HR for OS in heavier versus lighter women was 1.23 (95 % CI 1.07-1.42) for premenopausal women and 1.15 (95 % CI 1.06-1.26) for post-menopausal women, and the difference between the two groups was not significant (p = 0.57). Comparable pooled HRs for BCSS were 1.36 (95 % CI 1.20-1.54) for ER/PgR positive cancers and 1.46 (95 % CI 0.98-2.19) for ER/PgR negative cancers; and 1.18 (95 % CI 0.82-1.70) for pre-menopausal women and 1.38 (95 % CI 1.11-1.71) for post-menopausal women, also without significant group differences. Results were similar after adjustment for BMI measurement technique, years of follow-up, or study design. These findings led us to conclude that there is no evidence showing that the association of obesity with breast cancer outcome differs by hormone receptor or menopausal status. This has implications for studies of weight loss interventions in the adjuvant BC setting.