Association of Obesity With Breast Cancer Outcome in Relation to Cancer Subtypes: A Meta-Analysis

Abstract

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 or overweight at diagnosis of nonmetastatic 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 up to January 1, 2019. Study eligibility was performed independently by 2 authors. Studies reporting hazard ratios (HRs) of OS and/or DFS for obesity or overweight in BC subtypes were included. The pooled hazard ratio was computed and weighted using generic inverse variance and random effects models.

Results: Twenty-seven studies were included. Obese compared with nonobese 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 nonobese 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.

Figure 1.

Flow diagram. ASCO = American Society of Clinical Oncology; BC = breast cancer; BMI = body mass index; ESMO = European Society for Medical Oncology; HR = hazard ratio; OR = odds ratio; SABCS = San Antonio Breast Cancer Symposium.

Figure 2.

Association of obesity with disease-free survival (DFS) and overall survival (OS) in relation to breast cancer (BC) subtypes: hormone receptor positive and HER2 negative (HR+HER2−), HER2 positive (HER2+), and triple negative. A) Association of obesity at breast cancer diagnosis with DFS in HR+HER2− BC is shown. B) Association of obesity at BC diagnosis with OS in HR+HER2− BC is shown. C) Association of obesity at BC diagnosis with DFS in HER2+ BC is shown. D) Association of obesity at BC diagnosis with OS in HER2+ BC is shown. E) Association of obesity at BC diagnosis with DFS in triple-negative (TN) BC is shown. F) Association of obesity at BC diagnosis with OS in TNBC is shown. BMI = body mass index; CI = confidence interval; IV = inverse variance; SE = standard error.

Figure 3.

Association of obesity with breast cancer (BC)–specific survival in relation to BC subtypes. Results for (A) hormone receptor-positive and HER2 negative (HR+HER2−), (B) HER2 positive (HER2+), and (C) triple-negative BC subtypes are shown. BMI = body mass index; CI = confidence interval; IV = inverse variance; SE = standard error.