Presenters: Nick Crozier, PharmD, BCPS, Pharmacy Director, UNM Cancer Center, UNM Comprehensive Cancer Center; Ronald Kittson, PharmD, Clinical Pharmacy Supervisor, UNM Comprehensive Cancer Center
Co-Authors: Lisa Anselmo, PharmD, BCOP, Clinical Pharmacy Director, Pharmacy, UNM Hospitals; Branda Chalenunphonh, Student Pharmacist, UNM College of Pharmacy
Background: Body surface area (BSA) is used to calculate individual doses for chemotherapeutic agents.1 Default BSA calculation equations vary between e-prescribing platforms. At the University of New Mexico Comprehensive Cancer Center (UNMCCC) our e-prescribing platform used DuBois & DuBois; however, because of the complexity of the DuBois & DuBois equation, our nurses and pharmacists use Mosteller. To improve safety, we changed our e-prescribing platform calculation to Mosteller.
Objective: To determine whether switching BSA calculation from DuBois & DuBois to Mosteller results in clinical differences in dose or in outcomes for patients receiving chemotherapy.
Methods: The UNMCCC switched from the DuBois & DuBois to Mosteller BSA calculation on July 6, 2020. We collected data that included changes in BSA, therapeutic dose changes, and adverse event reporting. We extracted data for all chemotherapeutic agents that required BSA dosing between May 1, 2020, and August 10, 2020, to compare chemotherapy doses given to patients before and after the calculation switch date. Patients who received the same chemotherapeutic agent as part of the same regimen at least once before and after July 6, 2020, were included. Only the latest chemotherapy dose before July 6, 2020, and the earliest dose after July 6, 2020, were evaluated. We used each patient’s most recent height and weight before July 6, 2020, to calculate predicted Mosteller BSA. Finally, we examined individually all dose increases by ≥5%, for safety.
Results: A total of 227 patients who received a total of 367 doses were evaluated. In all, 234 doses had no change, 10 doses increased by 5% to 10%, and 6 doses increased by >10%. We calculated the predicted patient BSA change corresponding to 330 of the doses. Of the predicted BSA changes, 23% were expected to increase by ≥2.5% and 6.67% were expected to increase by 5% to 10%. Predicted BSA changes correlated poorly with dose changes (r2 = 0.0058). Most doses remained unchanged because of physician manual calculations, use of previous BSA option, and pharmacist dose adjustment and rounding. Dose increases of >10% were caused by changes in the patient’s weight and provider’s chemotherapy regimen adjustment. There were no adverse events reported or safety concerns.
Conclusion: Switching the e-prescribing platform BSA calculation from DuBois & DuBois to Mosteller resulted in an overall increase in our patients’ calculated BSA, without significant clinical impact on the patients’ dose or outcome. The change from DuBois & DuBois to Mosteller can be safely made in clinical practice for patients receiving active chemotherapy.
- Fancher KM, Sacco AJ, Gwin RC, et al. Comparison of two different formulas for body surface area in adults at extremes of height and weight. J Oncol Pharm Pract. 2016;22:690-695.