Real-world utilization of docetaxel among men with de novo metastatic castration-sensitive prostate cancer: A population-based study in men aged 66 or older.

47 Background: Docetaxel was the first agent, when added to androgen deprivation therapy (ADT), to demonstrate a survival benefit in men with metastatic castration-sensitive prostate cancer (mCSPC). It remains an important guideline recommendation approach in these men. However, real-world experience among patients with de novo metastatic disease is poorly understood. Using population-based data from Ontario Canada, we examined the real-world experience of using docetaxel in mCSPC. Methods: Men aged 66 years and older diagnosed with de novo metastatic prostate cancer between 2014-2019 were captured. The Cancer Activity Level Reporting system tracks information regarding the use of cancer treatments, including details of systemic therapy. We identified patients who received docetaxel intensification to ADT following diagnosis of de novo mCSPC and analyzed the proportion of patients who completed 6 cycles of treatment, required a dose decrease, and who visited the emergency department (ED) or were hospitalized for febrile neutropenia. Results: Over the 5-year study period, 399 men received docetaxel treatment among 3,556 identified with de novo mCSPC. The median age was 72 (IQR 68-76) and mean Charlson comorbidity index was 0.15 (SD +/- 0.72). Of the 399 men, 230 (58%), 202 (51%) and 175 (44%) patients completed at least 4, 5 and 6 cycles of docetaxel, respectively. Dose reduction during docetaxel treatment was required in 173 (43%) patients. Filgrastim was prescribed among 29 (7.3%) patients. Hospitalization or ED visit for febrile neutropenia was observed in 63 (16 %) of patients who received docetaxel. Conclusions: Among men age 66 years and over who received docetaxel and ADT for mCSPC, less than half were able to complete all six prescribed cycles. In addition, over two fifth required dose reductions and 16% experienced febrile neutropenia requiring hospitalization or ED visit. These data highlight the differences in expected outcomes between clinical trial populations (as reported in CHAARTED) and routine use.