Pattern of chemotherapy dosing in obese patients in a community hospital.

Abstract

e13099 Background: Obesity has increased to epidemic proportions, with 32.2% of US adults aged 20 years or older classified as obese (body mass index ≥ 30 mg/m2). In view of altered pharmacokinetics and possible excessive toxicity in obese patients, chemotherapy dose reductions are often employed in treating obese cancer patients. To our knowledge, there are no reports in the literature identifying patients who should have empiric dose adjustment because of obesity or the best method of dosing chemotherapy to standardize drug exposure in patients with varying degrees of obesity. As practice varies among institutions, we carried out a retrospective study to evaluate the chemotherapy dosing pattern in our obese patient population. Methods: Charts of patients who received chemotherapy at our institution during the year 2010 were reviewed. Data on age, height, weight, type and stage of cancer, date of chemotherapy, and type and dose of chemotherapy were retrieved from chart review. Only details of the first chemotherapy cycle at our institution were collected. Body surface area (BSA) was calculated by using the Mosteller formula. Independent samples t-test and Pearson chi-square statistics were used to investigate the difference between the means and proportions respectively. Results: Data from 191 patients were analyzed. Distributions (mean and range) of age, height, weight, body mass index (BMI) and BSA were 60 years (26 - 88), 65 inches (53 - 79), 166 pounds (90 - 340), 27.44 kg/m2 (14.52 - 56.57) and 1.85 m2 (1.36 - 2.66), respectively. Patients who had a full dose (n = 164) had a mean BMI of 27 kg/m2 (standard deviation (SD) 6.5) and a mean BSA of 1.82 m2 (SD 0.24) whereas those with a reduced dose had BMI (n = 27, mean 30.2, SD 7.1) and BSA (mean 1.97, SD 0.25). There is a significant difference between the means of the two groups (full dose and reduced dose) in terms of both BSA and BMI (p = 0.033 and p = 0.01, respectively). Significantly higher proportion of patients with BSA ≥ 2 received reduced dose compared to those with BSA < 2 (14 out of 48 (20.3%) versus 13 out of 143 (9%), p = 0.001). Conclusions: Patients with BSA ≥ 2 were more likely to get empiric chemotherapy dose adjustment at our institution. Further studies on chemotherapy dosing in obese patients are warranted.