Obesity linked to shorter DFS, OS across breast cancer subtypes
Obesity appeared associated with modestly shorter DFS and OS across breast cancer subtypes, according to a study published in Journal of the National Cancer Institute.
Researchers also noted significant associations of obesity with shorter breast cancer-specific survival among women with hormone receptor-positive/HER2-negative and triple-negative disease.
“We conducted a literature-based meta-analysis with the goal of clarifying the association of body size with outcomes in nonmetastatic [breast cancer] across the spectrum of immunohistochemically defined breast cancer subtypes in women receiving modern adjuvant therapies,” Ana Elisa Lohmann, MD, PhD, medical oncologist, cancer researcher and assistant professor at University of Western Ontario, and colleagues wrote. “Our main analysis compared DFS and OS in obese and nonobese groups, accepting obesity as defined in each study.”
Previous meta-analysis of obesity and breast cancer outcomes did not focus on disease subtypes, and limited or inconsistent evidence existed regarding associations in more aggressive subtypes, the researchers wrote.
Lohmann and colleagues examined associations of obesity or overweight at diagnosis of nonmetastatic breast cancer with survival outcomes in three subtypes: hormone receptor-positive/HER2-negative, HER2-positive and triple-negative disease.
Their analysis included 27 studies (n = 108,908) — 21 of which were observational and six interventional — that met eligibility criteria and reported HRs of OS and/or DFS for obesity and overweight in breast cancer subtypes. The researchers used generic inverse variance and random effects models to calculate and weight pooled HRs. They also performed a sensitivity analysis limited to studies with obesity defined as BMI of 30 kg/m2.
Results showed shorter DFS and OS among women with vs. without obesity in all breast cancer subtypes, including hormone receptor-positive/HER2-negative disease (HR for DFS = 1.26; 95% CI, 1.13-1.41; HR for OS = 1.39; 95% CI, 1.2-1.62); HER2-positive disease (HR for DFS = 1.16; 95% CI, 1.06-1.26; HR for OS = 1.18; 95% CI, 1.05-1.33); and triple-negative disease (HR for PFS = 1.17; 95% CI, 1.06-1.29; HR for OS = 1.32, 95% CI, 1.13-1.53).
Although overweight was associated with shorter OS for hormone receptor-positive/HER2-negative disease (HR = 1.14, 95% CI, 1.07-1.22), it did not appear associated with either DFS or OS in HER2-positive disease (HR for DFS = 1.02; 95% CI, 0.81-0.28; HR for OS = 0.96; 95% CI, 0.76-1.21) or triple-negative disease (HR for DFS =1.04; 95% CI, 0.93-1.18; HR for OS = 1.08; 95% CI, 0.81-1.44.)
“Additional research examining associations of overweight in all breast cancer subtypes is needed,” Lohmann and colleagues wrote. “Evaluation of HER2 status in the large adjuvant aromatase inhibitor trials would be of particular interest, as that would allow investigation of obesity associations in large groups of women with [hormone receptor-positive/HER2-negative] as well as [hormone receptor-positive/HER2-positive breast cancer].”
Among limitations, researchers noted few studies reported obesity associations according to menopausal status, and a meta-analysis of obesity associations across breast subtypes by menopausal status was not feasible aside from three studies in triple-negative breast cancer.
“Some caution is needed in interpreting results of breast cancer-specific survival analyses, particularly in the HER2-positive subtype, because fewer studies reported this outcome,” Lohmann and colleagues wrote. “This is an important outcome because it excludes obesity-related deaths that are not due to breast cancer — future studies should prioritize this outcome.”
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