Commentary on: “Effect of obesity on survival in women with breast cancer: systematic review and meta-analysis” (Melinda Protani, Michael Coory, Jennifer H. Martin)

Excerpt

Obesity was first associated with breast cancer outcomes in 1976; since that time, more than 50 reports have examined this association, and two meta-analyses have been published [1, 2]. The majority of the individual studies and both previous meta-analyses have provided evidence consistent with an increased risk of recurrence and/or death in obese versus non-obese women, with many hazard ratios (HRs) in the range of 1.5–2.0 in obese women. The recent meta-analysis by Protani et al. [3], with a specific focus on overall and breast cancer specific survival, represents a major update of previous work. This literature-based meta-analysis included 43 studies (38 observational cohorts and 5 treatment cohorts) conducted primarily in westernized countries. A total 36 studies provided information on all cause survival and 19 on breast cancer specific survival. Pooled HRs of 1.33 comparing obese to non-obese women were identified for both outcomes [95% confidence intervals (CIs) excluded one for both outcomes], consistent with a significant adverse effect of obesity. HRs associated with obesity were larger in premenopausal than in postmenopausal women (HR 1.47, 1.22, respectively), in observational versus treatment cohorts (HR 1.36, 1.22, respectively) and in studies published after 1995 versus earlier (HR 1.49, 1.31 respectively); none of the differences between these pairs of HRs was statistically significant. HRs varied minimally (and non-significantly) depending on whether body size was classified using body mass index (BMI) or waist–hip ratio. …