Docetaxel dose-intensity effect on overall survival in patients with metastatic castrate-sensitive prostate cancer

Several studies assessed the association of docetaxel dose intensity (DI) and efficacy in metastatic castrate-resistant prostate cancer (mCRPC) patients with contradicting conclusions. In this retrospective analysis, we will assess whether the docetaxel DI used in patients with metastatic castrate-sensitive prostate cancer (mCSPC) is associated with overall survival (OS).

All patients with mCSPC treated at The Ottawa Hospital Cancer Centre that received docetaxel chemotherapy between June 2014 and September 2017 were identified. The association between relative dose intensity (RDI) and OS was assessed using univariate and multivariable Cox model adjusting for age, Gleason score, burden of disease, visceral involvement, de novo metastases and baseline prostate-specific antigen (PSA).

Eighty-one patients were included in the analysis. Only 35 patients (43%) were able to complete the planned treatment with a RDI of at least 90%. On a univariate analysis, higher RDI and number of cycles of docetaxel received were associated with longer OS. For every 10% decrease in RDI, the risk of death increased by 23% (HR 1.23, 95% CI 1.09-1.4, P = 0.001). For every increment of one cycle (and up to six), the risk of death decreased by 27% (HR 0.73, 95% CI 0.61-0.88, P = 0.001). On multivariate analysis, reduced RDI was the only predictor significantly associated with OS (HR 1.18, 95% CI 1.02-1.36, P = 0.026).

Our study suggests that in mCSPC, reduced docetaxel RDI is associated with shorter survival. Unnecessary dose reductions, treatment delays and early discontinuation should be avoided. Granulocyte colony-stimulating factor may be considered to maintain standard DI.