Impact of Body Mass Index and Actual Weight Based Neoadjuvant Chemotherapy Doses on Pathologic Complete Response in Operable Breast Cancer

Abstract Introduction The impact of body mass index (BMI) and chemotherapy dose reduction on pathologic complete response (pCR) following neoadjuvant chemotherapy (NAC) for locoregional breast cancer remains unclear. Contemporary studies have reported largely on trial populations and utilized dose capping. Methods Patient registries at the University of Iowa were queried to identify patients with operable breast cancer who received NAC. Dose reductions were calculated for taxanes (T), anthracyclines (A) and non-A-T chemotherapy. Clinical-pathologic characteristics, chemotherapy dose reductions and adverse events were compared between normal (BMI < 25 kg/m2 ) and overweight-obese patients (BMI ≥ 25 kg/m2 ). Additionally, the synergistic effect of BMI and chemotherapy dose reduction on pCR was assessed. Results Of 171 eligible patients, 112 were overweight-obese. Chemotherapy dosing was capped in two patients; all others initiated full weight-based treatment. Overweight-obese patients required more frequent taxane (44.6% vs 25.4%, p=0.01) and any chemotherapy dose reductions (50.5% vs 33.9% p=0.03). pCR was attained in 29.2% of patients. In a multivariable model, the interaction term for BMI as a continuous variable and any chemotherapy dose reduction was significant independent of the clinical stage and tumor receptor status (p = 0.04). For obese patients, any chemotherapy dose reduction was significantly associated with increased odds of not attaining pCR. Conclusion During NAC, overweight-obese patients more often have chemotherapy dose reductions. Chemotherapy dose reduction in obese patients was a powerful predictor of not attaining pCR. This was not seen for normal or overweight patients. Opportunities may exist to improve pCR rates in this higher risk group.