A higher body mass index (BMI) was associated with an elevated risk of breast cancer recurrence and worse survival in patients of African ancestry (AA), but not in those of European ancestry (EA), enrolled in a phase 3 trial.
The association was most significant among patients with severe obesity and those with estrogen receptor (ER)-positive breast cancer. These results were published in Cancer.
Both obesity and AA have been linked to worse survival after early-stage breast cancer, and the prevalence of obesity is disproportionately higher among AA patients. With this study, researchers sought to investigate the intersection between ancestry and obesity.
The researchers analyzed 2854 patients with high-risk, early-stage breast cancer enrolled in the phase 3 ECOG-ACRIN-5103 trial (ClinicalTrials.gov Identifier: NCT00433511) of adjuvant anthracycline and taxane-based chemotherapy, with or without bevacizumab.
Of 2854 patients analyzed, 2471 were genetically classified as EA and 383 as AA. In the AA population, 91.1% of patients self-identified as Black, 8.1% as White, 0.5% as Native American, and 0.3% as Asian. In the EA population, 99.8% identified as White and 0.1% as Black.
The mean BMI was higher in the AA population (32.3 kg/m2) than in the EA population (29.4 kg/m2). Patients in the AA population were more likely to have class 3 severe obesity (15.4%) than those in the EA population (8.5%).
At a median follow-up of 47.8 months, there were 427 disease-free survival (DFS) events and 216 deaths in the overall cohort.
In a multivariate analysis, a higher BMI was significantly associated with worse DFS (hazard ratio [HR], 1.25; 95% CI, 1.07-1.46; P =.0042) and overall survival (OS; HR, 1.38; 95% CI, 1.10-1.73; P =.0054) in AA patients but not in EA patients (DFS, P =.5; OS, P =.52).
When patients were analyzed by BMI categories, there was a strong association between severe class 3 obesity (BMI ≥40) and worse DFS (HR, 2.04; P =.008) and OS (HR, 2.21; P =.043) in AA patients. Severe obesity did not affect DFS (P =.82) or OS (P =.28) in the EA patients.
Triple-negative breast cancer was more common among AA patients (49.2%) compared with EA patients (36.4%). However, in the subgroup analysis of patients with ER-positive and triple-negative breast cancer, the most significant association between BMI and worse outcomes was found in AA patients with ER-positive disease (DFS HR, 1.34; OS HR, 1.60).
Overall, the study showed a strong association between higher BMI and worse outcomes for AA patients, particularly for those with severe class 3 obesity and ER-positive disease. The researchers suggested that the degree of obesity and adiposity may have a variable influence on physiologic metabolic processes by race.
“These observations help define optimal populations for weight change interventions designed to affect disparities and survival in early-stage breast cancer,” the researchers concluded.
Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.
Ballinger TJ, Jiang G, Shen F, Miller KD, Sledge GW, Schneider BP. Impact of African ancestry on the relationship between body mass index and survival in an early-stage breast cancer trial (ECOG-ACRIN E5103). Cancer. Published online March 14, 2022. doi:10.1002/cncr.34173