4CPS-267 Retrospective analysis of carboplatin dosing prescribed in a chemotherapy regimen and its relationship with toxicity

Background and importance Carboplatin is one of the antineoplastics in which the dose must be adjusted according to the glomerular filtration rate (GFR) and the area under the curve (AUC). The Cockroft–Gault equation is the most widely used for the calculation of GFR and the Calvert formula is the most commonly used for carboplatin dosing. The Cockroft–Gault equation has two variables (weight and serum creatinine) that depend on the body composition of the patient, and therefore overweight and cachectic people are at risk of undergoing inappropriate carboplatin dosing. Aim and objectives To analyse carboplatin dosage in cancer patients to determine whether they are over or underdosed in comparison with the theoretical dose during the first cycle, and to determine the relationship between the dosage received in this cycle and dose reduction in subsequent cycles, as a result of side effects. Material and methods This was a retrospective analysis of prescriptions of chemotherapy with carboplatin conducted in 2019. The variables collected were: anthropometric data (age and sex), number of cycles, chemotherapy scheme, diagnosis, analytical data and dose of carboplatin prescribed based on the AUC of the scheme. They were used as tools to support pharmaceutical validation: creatinine clearance (CrCl) according to the Cockroft–Gault equation and Calvert formula. The mean per cent error (MPE) was used to determine the relationship between the dose received and the theoretical dose calculation during the first cycle. The Shapiro–Wilks test was used to see if the cohort was parametric and the Mann–Whitney U test to assess the possible relationship between the patient’s dosage during the first cycle and dose reduction in subsequent cycles. Results 50 patients were selected, 84% were men and mean age was 66.72±6.66 years. After assessment, 25 patients (50%) received higher doses than the theoretical dose calculation. The mean MPE value (with standard error) for this group was 15.88 ±2.7%. In total, six patients in this group underwent dose reduction due to toxicity related to overdose. No link was found with dose reduction in subsequent cycles for this cohort of patients after performing statistic analyses. Conclusion and relevance Not using adjusted body weight in obese patient or capping the level of serum creatinine in cachectic patients (0.7–0.8 mg/dL) may lead to incorrect doses of carboplatin and subsequent toxicity (neutropenia and thrombocytopenia). References and/or acknowledgements Conflict of interest No conflict of interest