Chemotherapy under-dosing in obese endometrial cancer patients.

Abstract

e17124 Background: Although concerns exist regarding toxicity and overdosing of chemotherapy when using actual body weight in obese patients, current recommendations are to use full weight-based chemotherapy doses without a cap at a body surface area (BSA) = 2.0m2. We sought to determine the frequency of full weight-based chemotherapy dosing in obese compared to overweight endometrial cancer patients. Methods: We performed a retrospective cohort study on obese and overweight surgically-managed EC patients who received carboplatin (CB) and paclitaxel (P) as adjuvant chemotherapy at a single institution between 2006-2011. Obesity was defined as a BMI ≥ 30kg/m2 and overweight as a BMI ≥ 25kg/m2. Demographic and pathologic data, as well as adjuvant chemotherapy dosing (using either Jeliffe or Cockcroft-Gault adjusted body weight [for CB]) or a BSA cap at 2.0m2 [for P]), height, weight and BSA at initial cycle were abstracted. Estimated full-weight based chemotherapy dosing (calculated using the Cockcroft-Gault actual body weight [for CB] or DuBois BSA formula without a cap at 2.0m2 [for P]) was calculated and compared to the actual dosing documented in the medical records. Descriptive statistics were performed, with data compared using Wilcoxon-sign-rank tests. Results: 31 obese (59.6%) and 21 overweight (40.4%) women underwent adjuvant chemotherapy with CB/P. The median age was 66.6 years (IQR 61.3-73.7yr), 50% were stage III and IV disease and 68.8% were grade 3 histology. For obese patients, 32.26% received limited paclitaxel doses and 90.32% were under-dosed with carboplatin when using actual body weight. For overweight patients, 47.6% received limited paclitaxel doses and 61.9% were under-dosed with carboplatin. Chemotherapy under-dosing was statistically significant when comparing obese to overweight patients receiving carboplatin (p = 0.018) but not paclitaxel (p = 0.264). Conclusions: Obese and overweight endometrial cancer patients are frequently under-dosed with chemotherapy when weight-based dosing is not utilized. The degree of chemotherapy under-dosing is significantly higher in obese compared to overweight patients receiving carboplatin, which may limit the quality of care and oncologic outcomes in this patient population.