Multivariable analysis of predictors of side effects of cabazitaxel in the Italian Expanded Access Program.

Abstract

225 Background: Cabazitaxel-based chemotherapy provides a survival benefit after docetaxel failure in patients with prostate cancer. Grade 3-4 neutropenia and febrile neutropenia were relatively frequent in the registrative trial, but their incidence in clinical practice is likely to be lower, as shown by data collected in the Expanded Access Program (EAP). While cumulative doses of docetaxel are associated to neuropathy, the effect of cumulative doses of cabazitaxel is unknown. In this study, we assessed 'per cycle' incidence and predictors of toxicity in the Italian cohort of the EAP, with a focus on the effect of cumulative doses of cabazitaxel. Methods: The study population consisted of 218 Italian patients enrolled in the cabazitaxel EAP. The influence of selected variables on the most relevant side effects identified was assessed using a Generalised Estimating Equations (GEE) model at univariate and multivariate analysis. Multivariate logistic regression analysis was performed using a backward selection procedure. Variables with a p value ⩽0.1 were kept in the final model. Results: Per cycle incidence of grade 3-4 neutropenia was 8.7%, while febrile neutropenia occurred only in 0.9% of cycles and was an early event, occurring during the first three cycles only. Multivariate logistic regression analysis showed that the odds of having grade 3 – 4 neutropenia, febrile neutropenia and anemia were statistically significantly reduced by 10, 48 and 7%, respectively, every 10 mg/m2 increase of total prior dose of cabazitaxel. Interestingly, a body surface area > 2 m2 was associated to increased odds of having grade 3-4 neutropenia. In this regard, it must be noted that all patients with body surface area > 2 m2 had their total dose capped to 50 mg, with a mean (95% CI) and median (IQR) dose reduction of 7.1 (7.58-6.69) and 5.9 (2.76-10.27) % with respect to planned dose. Conclusions: Cumulative doses of cabazitaxel are associated to decreased risk of bone marrow toxicity. Patients with body surface area >2 m2 are at increased risk of bone marrow toxicity and dose capping should be considered. These data indicate that cabazitaxel should not be arbitrarily suspended because of concerns of cumulative toxicity.