Purpose: The American Society of Clinical Oncology (ASCO) panel of experts published recommendations in 2012 indicating that full weight-based cytotoxic chemotherapy doses should be used to treat obese patients, particularly when the goal of treatment is cure. A formal evaluation of how chemotherapy is dosed in obese patients at the Boise VAMC in Idaho was warranted to determine the frequency of weight-based dosing of chemotherapy for obese adult patients with cancer, and to determine whether there was a need to implement a standardized weight-based dosing and monitoring policy.
Methods: This was a retrospective review of patient electronic records within the Boise VAMC who initiated chemotherapy from May 1, 2012, to September 5, 2013. Demographic data (age and sex), ECOG performance status, intended treatment protocol, type and stage of cancer, and treating medical oncologist were obtained from electronic records for the patient’s first visit with the Boise VA oncology department. Indications for chemotherapy were identified from the medical record and categorized as either curative or palliative. The height, weight, and calculated body surface area (BSA) and body mass index (BMI) were obtained from electronic chart on the closest date to which chemotherapy orders were written prior to the first cycle of chemotherapy. Criteria for evaluating weight-based vs non-weight-based chemotherapy doses were based on recommended dosing, using actual body weight. Dosing was considered weight-based if the prescribed dose was within +10% of the recommended weight-based dose. Electronic charts were reviewed further to determine frequency of withholding or delaying subsequent chemotherapy doses and the type of adverse events (AEs) after the first cycle. Any AE or allergy was noted if it affected subsequent chemotherapy dosing.
Results: Fifty-nine patients were reviewed. The majority of patients were male and elderly with an average BMI of 30.59 (+ 5.2). Patients receiving non-weight-based dosing regimens had a significantly higher mean BMI and BSA than those receiving weight-based dosing regimens (P = .003). Significantly more patients received weight-based dosing when goal of treatment was curative compared with palliative (P = .01). Of the patients who were overweight and obese, 69.4% of chemotherapy doses were based on actual body weight. A higher proportion of curative/adjuvant regimens were weight-based compared with palliative (P < .001). Ninety percent (n = 18) of patients with a goal of cure received weight-based regimens. No statistically significant differences were identified in patients with subsequent doses delayed or withheld. However, there was a trend for patients receiving non-weight-based regimens to have the second dose withheld more often. The percentage of patients with documented adverse drug events (ADEs) was modest and not significantly different between groups. There was an overall trend in increases of weight-based dosing, although not statistically significant.
Conclusions: In this formal evaluation of chemotherapy dosing in overweight and obese patients at the Boise VAMC, a large majority of doses were weight-based in this patient subset (69.4%), especially when the goal of therapy was curative/adjuvant (91.9%). Documented ADEs were relatively infrequent and mainly consisted of myelosupression. Overall, there is likely not a need to implement a standardized weight-based dosing and monitoring policy that incorporates weight-based dosing at the Boise VAMC.