Grant: Project Grant

The standard treatment for metastatic prostate cancer is androgen deprivation therapy (ADT) and androgen receptor pathway inhibitors (ARPI). However, for some patients, their cancer cells do not respond to this treatment. Currently, some cancer doctors recommend adding a chemotherapy called docetaxel to the standard treatment when the cancer has aggressive features indicating that some cells are becoming resistant to the hormone therapy. Other cancer doctors prefer to leave docetaxel treatment until later when the cancer is growing to avoid early side effects. While docetaxel chemotherapy does improve how long patients live on average with metastatic prostate cancer, we are not sure who benefits the most from docetaxel and when it is best to receive it. We believe the best time to offer docetaxel may be about 6-12 months after receiving hormone therapy (ADT + ARPI). We will use a blood test, the prostate-specific antigen (PSA), to gauge how well the cancer is responding to standard treatment. Patients with a PSA 0.2 or less will not be eligible for this trial as they are likely to continue to benefit from hormone therapy for many years. However, patients with a PSA >0.2 after 6 months of hormone treatment will be offered this study because there is a higher chance their cancer will worsen in the next year and, on average, live only 3 years. Eligible patients will be randomly selected to receive either 6 treatments of docetaxel in addition to their hormone therapy or continue their current hormone therapy without docetaxel. The goal of this study is to determine if early treatment with docetaxel extends a patient's life. Other goals include determining if: 1) patients' cancers are sensitive to hormone therapy for longer, 2) patients have good or improved long-term quality of life after docetaxel, and 3) a new blood test (circulating tumour DNA) improves how we decide who benefits the most from docetaxel.