Background
Obesity at breast cancer (BC) diagnosis has been associated with poor outcome, although the magnitude of effect in different BC subtypes is uncertain. We report on the association of obesity/overweight at diagnosis of non-metastatic BC with disease-free (DFS) and overall survival (OS) in the following defined subtypes: hormone receptor positive/HER2 negative (HR+HER2-), HER2 positive (HER2+), and triple negative (TNBC).
Methods
We searched MEDLINE, EMBASE and COCHRANE databases until January 1, 2019. Study eligibility were performed independently by two authors. Studies reporting hazard ratios (HR) of OS and/or DFS for obesity/overweight in BC subtypes were included. Pooled HR were computed and weighted using generic inverse variance and random effects models.
Results
27 studies were included. Obese, compared to non-obese, women, had worse DFS in all subtypes: the hazard ratios were 1.26 (95% confidence interval [CI] = 1.13 to 1.41, P < .001) for HR+HER2-BC, 1.16 (95%CI = 1.06 to 1.26, P < .001) for HER2+ BC, and 1.17 (95%CI = 1.06 to 1.29, P = .001) for TNBC. OS was also worse in obese vs non-obese women (HR+HER2-BC HR = 1.39, 95%CI = 1.20 to 1.62, P < .001; HER2+BC HR = 1.18, 95%CI = 1.05 to 1.33, P = .006 and TNBC HR = 1.32, 95%CI = 1.13 to 1.53, P < .001). As opposed to obesity, overweight was not associated with either DFS or OS in HER2+BC (HR = 1.02, 95%CI = 0.81 to 1.28, P = .85; and HR = 0.96, 95%CI = 0.76 to 1.21, P = .99, respectively) or TNBC (HR = 1.04, 95%CI = 0.93 to 1.18, P = .49; and HR = 1.08, 95%CI = 0.81 to 1.44, P = .17), respectively. In HR+HER2-BC, being overweight was associated with worse OS (HR = 1.14, 95%CI = 1.07 to 1.22, P < .001).
Conclusions
Obesity was associated with modestly worse DFS and OS in all BC subtypes.
