Background: Carboplatin dosing for gynecologic malignancies is traditionally based on the Jelliffe formula that lacks dose adjustment for weight. Obese women may therefore receive a sub-therapeutic carboplatin dose. This study assessed the association between BMI and outcome for ovarian cancer patients treated with carboplatin-based chemotherapy.
Methods: An analysis of patients treated with carboplatin and paclitaxel on Gynecologic Oncology Group (GOG) protocol 158 was performed. The dose of carboplatin for each patient was based on an area under the curve of 7.5 and a glomerular filtration rate (GFR) derived from the Jelliffe formula which is derived from age and serum creatinine. Patients were stratified based on body mass index (BMI).
Results: A total of 387 patients were included in the analysis. The patients were stratified into three groups: normal weight (BMI<25.0, 50%), overweight (BMI 25-29.9, 32%) and obese (BMI > or = 30.0, 18%). Compared to pretreatment values, the obese patients had a lower relative decrease in their platelet counts (-25% for BMI > or = 30 vs. -61% for BMI<25) (p = 0.01). Similar trends were noted for relative changes in hemoglobin (p = 0.006) and hematocrit (p = 0.002). Dose reductions were required in 34% of normal weight compared to 21% of the obese women (p = 0.004). There was a trend toward increased risk for disease progression in women with a BMI > or = 30 (RR: 1.25, 95% CI: 0.93-1.69, p = 0.14).
Conclusion: Obese ovarian cancer patients treated with carboplatin experience substantially less toxicity than normal weight women. The lower toxicity suggests that obese patients may be receiving a substandard drug dose.