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

Abstract

Introduction: The effect of body mass index (BMI) and chemotherapy dose reduction on pathologic complete response (pCR) after neoadjuvant chemotherapy (NAC) for locoregional breast cancer remains unclear. Contemporary studies have reported largely on trial populations and used dose-capping.

Patients and 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) and overweight/obese patients (BMI ≥25). 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 2 patients; all others initiated full weight-based treatment. Overweight/obese patients required more frequent taxane (44.6% vs. 25.4%; P = .01) and any chemotherapy dose reductions (50.9% vs. 33.9%; P = .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 = .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 might exist to improve pCR rates in this higher-risk group.

Keywords: BMI; Chemotherapy dosing; Dose capping; Neoadjuvant therapy; Taxane; Weight-based dosing; pCR.

Figure 1. Rate of Adverse Events Resulting in Taxane Dose Reduction According to Body Mass Index (BMI) Category^a

Abbreviation: GI = gastrointestinal. ^aNo significant difference between BMI groups were evidenced. Rates within the normal and overweight/obese were one the basis of 59 and 112 patients respectively.

Figure 2. Multivariable Regression Analyses of Clinical-Pathologic Factors and Odds Ratio (OR) of Not Attaining a Pathologic Complete Response (pCR)

Abbreviations: HR = hormone receptor; TNBC = triple negative breast cancer that did not express HR or HER2/neu.