Association of Body Mass Index with 21-Gene Recurrence Score among Women with Estrogen Receptor-Positive, ERBB2 -Negative Breast Cancer

Abstract

Importance: Body mass index (BMI) may affect the 21-gene recurrence score (RS) in patients with ER-positive, ERBB2-negative breast cancer. If high BMI increases genomic risk in ER-positive, ERBB2-negative breast cancer, weight control will become more important. Objective: To assess the association between RS and BMI according to age groups and address BMI as a factor associated with high RS. Design, Setting, and Participants: This cohort study included 2295 patients with ER-positive, ERBB2-negative breast cancer who had undergone a multigene assay between March 29, 2010, and December 31, 2020, in 2 hospitals. All of the study patients were Korean women, and the median follow-up period was 45 months (range, 1-40 months). The correlations between continuous RS and BMI were investigated. A high BMI was defined as a body mass index greater than or equal to 25. In the younger age group (age ≤45 years), a high RS was defined as an RS of greater than 20. Exposures: Body mass index. Main Outcomes and Measures: The Pearson correlation coefficient was used to estimate the association between RS and BMI. A multivariable binary logistic model was used to identify high RS. Results: Among the 2295 women included (mean [SD] age, 49.8 [4.00] years; range, 22-81 years), 776 were aged 45 years or younger; RS and BMI were weakly correlated (correlation coefficient, 0.119; P