Anthropometric, metabolic and molecular determinants of human epidermal growth factor receptor 2 expression in luminal B breast cancer.

Genomic and trascriptomic profiling has recently contributed details to the characterization of luminal B breast cancer. We explored the contribution of anthropometric, metabolic, and molecular determinants to the multifaceted heterogeneity of this breast cancer subtype, with a specific focus on the association between body mass index (BMI), pre-treatment fasting glucose, hormone receptors, and expression of human epidermal growth factor receptor 2 (HER2). Extensively annotated specimens were obtained from 154 women with luminal B breast cancer diagnosed at two Italian comprehensive cancer centres. Participants' characteristics were descriptively analyzed overall and by HER2 status (positive vs. negative). BMI (<25 vs ≥25), pre-treatment fasting glucose (<median value of 94 mg/dl vs. ≥94) and percentage of hormone receptors were tested for association with HER2 expression in regression models. In univariate models, BMI, fasting glucose and, at a lesser extent, percentage of estrogen receptors (ER) were significantly and inversely associated with HER2 expression (OR: 0.32, 95% CI: 0.16-0.66; 0.43, 0.23-0.82; 0.96, 0.94-0.97, respectively). The multivariate models confirmed the protective role of BMI and ER on HER2 expression, with luminal B HER2 positive patients being significantly less frequent among women within the highest category of BMI and percentage expression of ER compared with their counterparts (OR: 0.22, 95% CI: 0.09-0.53; 0.95, 0.93-0.97). In conclusions, BMI and percentage of ER representation are inversely associated with HER2 expression in luminal B breast cancers. Upon confirmatory findings, this might help identify patient subgroups who may best benefit from the use of interventions targeting insulin resistance in well depicted breast cancer scenarios.