Abstract PO-172: Impact of African ancestry on the relationship between body mass index (BMI) and survival in early stage breast cancer: Retrospective analysis from E5103

94 Background: Weight gain concerns breast cancer patients, can impact quality of life, may lead to therapy non-adherence, and is associated with increased recurrence risk and mortality. Early placebo-controlled trials did not identify a clear correlation between Tamoxifen (TAM) and weight gain; gain due to aromatase inhibitors (AIs) is not well characterized. We hypothesized that weight gain occurs more frequently than previously reported in breast cancer patients receiving endocrine therapy. Methods: This is a retrospective chart review investigating body mass index (BMI) change in women after breast cancer therapy. Patients with early stage breast cancer and whom had BMI and treatment data (at least 90 days) from 2003-2012 were identified in The Columbus Breast Cancer Tissue Bank. Patients were separated by treatment received: chemotherapy with and without endocrine therapy vs. endocrine therapy alone (including both TAM and AIs) vs. no other treatment. Results: A total of 970 subjects were included in the analysis. At diagnosis and/or treatment initiation, patients’ mean BMI was 29.2 ± 7.0 kg/m2; mean age 53.7± 11.6 years; and average length of therapy/follow up per patient, 1833 days (range 90-3,990). Patients who received an AI alone had significantly decreased BMIs during therapy (-0.65± 0.29 kg/m2, p = 0.025), whereas patients receiving chemotherapy alone, chemotherapy with TAM, or TAM followed by AI therapy, had significantly increased BMIs (0.51 ± 0.25, 0.73 ± 0.26, 1.01 ± 0.51 kg/m2; p = 0.039, 0.005, 0.045, respectively). Both older age and a higher BMI at diagnosis were associated with a significantly greater decline in BMI over treatment time (p < 0.001 and p < 0.001, respectively). In a multivariate regression model, after adjusting for age and initial BMI effect, the BMI change noted among different treatment groups was no longer significantly different (p = 0.43). BMI change was not statistically associated with treatment length (p = 0.26). Conclusions: Our review of a large, early stage breast cancer patient cohort showed no association between weight gain and endocrine therapy after adjusting for the effect of initial BMI and age at diagnosis. Additional study is needed to identify other factors impacting weight in this population.

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Impact of African ancestry on the relationship between BMI and survival in early stage breast cancer: Retrospective analysis from E5103.

Journal of Clinical Oncology ◽

10.1200/jco.2021.39.15_suppl.1010 ◽

2021 ◽

Vol 39 (15_suppl) ◽

pp. 1010-1010

Author(s):

Tarah Jean Ballinger ◽

Guanglong Jiang ◽

Fei Shen ◽

Kathy Miller ◽

Bryan P. Schneider

Keyword(s):

Breast Cancer ◽

Racial Disparities ◽

Early Stage ◽

African Ancestry ◽

Genetic Ancestry ◽

Early Stage Breast Cancer ◽

European Ancestry ◽

A Genome ◽

The Impact ◽

The Relationship

1010 Background: Both Black race and obesity are associated with worse survival in early stage breast cancer. Obesity disproportionately affects Black women; however, the degree this contributes to racial disparities in breast cancer remains unclear. Prior work evaluated heterogeneous populations or used self- reported race, rather than genetic ancestry. African ancestry is associated with higher BMI and worse survival in breast cancer; however, the intersection between genetic ancestry and obesity on survival outcomes remains unknown. Methods: We analyzed data from the adjuvant trial E5103. Patients with high risk, HER2 negative breast cancer received doxorubicin/cyclophosphamide x 4, followed by weekly paclitaxel x 12, with or without bevacizumab. Genetic ancestry was determined on the 2,854 patients with available germline DNA, BMI, and outcome data using principal components from a genome-wide array. The primary objective assessed impact of BMI on DFS and OS by ancestry. Multivariate Cox proportional hazard models evaluated correlation between continuous or binary BMI and survival in African (AA) and European (EA) Americans. Results: 13.4% of patients were genetically classified as AA and 86.6% as EA. Higher continuous BMI was significantly associated with worse DFS and OS only in AAs (DFS: HR = 1.25 95% CI 1.07-1.46, p = 0.004; OS: HR = 1.38 95% CI 1.10-1.73, p = 0.005); not in EAs (DFS HR = 0.97 95% CI 0.90-1.05, p = 0.50; OS HR = 1.03 95% CI 0.93-1.14, p = 0.52). By disease subtype, BMI was associated with worse outcomes only in AAs with ER+, and not TNBC. By categorical BMI, WHO class III obesity (³ 40) significantly associated with worse DFS and OS only in AAs (DFS HR = 1.98, p = 0.010; OS HR = 2.07, p = 0.064), not in EAs (DFS HR = 0.97, p = 0.86; OS HR = 1.28, p = 0.30). Proportion of African ancestry (proAA) was associated with higher BMI and worse outcomes in the total population; however, within AAs there was no significant interaction between proAA and BMI on DFS (HR = 0.36, p = 0.06) or OS (HR = 0.38, p = 0.24). In AAs, BMI remained associated with DFS (HR = 2.78, p = 0.019), suggesting higher BMI is associated with worse DFS regardless of proAA. Coefficients for the interaction term indicate that as proAA increases the impact of BMI on outcome is lessened. Conclusions: Higher BMI is significantly associated with worse breast cancer outcomes in women of African ancestry in E5103, but not in those of European ancestry. Categorically, this association was significant only for severe obesity, indicating the relationship may depend on the degree of obesity. As proAA increased in AAs, the impact of BMI on outcome was lessened, suggesting other host factors may contribute more to obesity’s influence on outcome than genetics. Determination of the optimal populations for weight loss interventions will advance precision medicine efforts to impact racial disparities and outcomes in early stage breast cancer.

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