Obesity elevates risk for distant recurrence, mortality in early-stage breast cancer
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Key takeaways:
- Higher BMI appeared linked to greater risk for distant recurrence among women with early-stage breast cancer.
- Results also showed an association between elevated BMI and mortality.
SAN ANTONIO — Elevated BMI increased risk for breast cancer mortality and distant recurrence among women with early-stage disease, according to findings presented at San Antonio Breast Cancer Symposium.
Researchers observed this association among women with BMI of 25 kg/m2 or higher, regardless of ER status, menopausal stage and other factors.
“Ten years ago, our preliminary analysis of part of this dataset generated two hypotheses that are now tested,” Hongchao Pan, MSc, PhD, statistician and epidemiologist in the clinical trial service and epidemiologic studies units, as well as associate professor at University of Oxford, said during a presentation. “Hypothesis one was there’s a somewhat less effect of BMI if postmenopausal than premenopausal? This hypothesis is now confirmed. Hypothesis two was that there’s zero effect of BMI in ER-negative disease. This hypothesis is now strongly contradicted.”
Background and methods
Pan and colleagues previously published work that showed obesity only had a significant association with breast cancer mortality among pre-/peri-menopausal women with ER-positive early-stage disease.
“Based on the far larger 2024 [Early Breast Cancer Trialists’ Collaborative Group (EBCTCG)] database, however, we can now test that unexpected finding and better characterize any relevance of patient characteristics to the association of BMI with distant recurrence and mortality,” researchers wrote in the abstract.
The analysis included 206,904 women (60% postmenopausal; 77% with ER-positive disease) with early-stage breast cancer. Study participants had BMI of 15 kg/m2 to 50 kg/m2 and had been entered into the EBCTCG database between 1978 and 2017.
Pan and colleagues categorized obesity as a BMI of 30 kg/m2 to 50 kg/m2; overweight as 25 kg/m2to less than 30 kg/m2; and lean as 15 kg/m2 to less than 25 kg/m2.
Mean BMI in the cohort was 27.1 kg/m2 (standard deviation = 5.6). About one-quarter (26%) had obesity, with obesity rates increasing from the early 1980s (19%) to the early 2010s (27%).
Associations between BMI and rates of distant recurrence and mortality served as the primary endpoint.
Results and next steps
Results showed a significant association between BMI increase of 5 kg/m2 and first distant recurrence (overall adjusted RR = 1.06; 95% CI, 1.05-1.07).
This association remained consistent among premenopausal women (RR = 1.08; 95% CI, 1.07-1.1) and postmenopausal women (RR = 1.05; 95% CI, 1.03-1.06).
Researchers observed an association between BMI and first distant recurrence regardless of tumor characteristics, adjuvant therapy receipt, year of diagnosis, time since diagnosis, and ER status.
Compared with women classified as lean, results showed RRs for first distant recurrence of 1.17 (95% CI, 1.14-1.2) among women with obesity and 1.07 (95% CI, 1.04-1.1) among those with overweight.
The association between BMI and breast cancer mortality appeared consistent with the association observed between BMI and distant recurrence.
Researchers suggested future studies explore whether weight loss interventions, including GLP-1 receptor agonists, reduce risk for recurrence or mortality among women with early breast cancer and elevated BMI.
“Our data indicates a strong association between BMI and breast cancer prognosis,” Pan told Healio. “If you want to avoid a 2% increase in 10-year rates of distant recurrence, you would need to reduce your BMI by 12 units — that’s really big. Even [to reduce risk by 1%], you need to reduce BMI by 5 units, which still isn’t achievable for many. In the future, I think it may be feasible to factor anti-obesity medication into ongoing randomized trials of adjuvant therapy.”
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Pan H, et al. Abstract GS2-09. Presented at: San Antonio Breast Cancer Symposium; Dec. 10-13, 2024; San Antonio.
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