Study of Pembrolizumab (MK-3475) Combination Therapies in Metastatic Castration-Resistant Prostate Cancer (MK-3475-365/KEYNOTE-365)

To join this study, you must be an adult male, at least 18 years old, and have prostate cancer that has spread to other parts of your body and is no longer responding to hormone therapy (mCRPC). The type of prostate cancer also matters; most participants need to have a specific type called adenocarcinoma. For some parts of the study, people with a rare type of prostate cancer that has neuroendocrine cells might be able to join.

Doctors will also need to review your past medical records and possibly take a tissue sample (biopsy) from your cancer, if it hasn't been from an area that was previously treated with radiation. This helps them understand your cancer better and make sure the study treatment is suitable for you. You must also have shown that your prostate cancer has recently worsened or progressed, which might be seen through blood tests (like PSA levels) or scans.

Importantly, your doctor will check many other detailed criteria to ensure you are a good fit for the study and that it's safe for you to participate. If your cancer type doesn't quite fit, or if you've had certain previous treatments, you might not be eligible for certain parts of the study.

If you are eligible and choose to take part in this study, you would receive the assigned study medications directly from the research team. These treatments are given in different ways, such as intravenous infusions (through a drip into a vein) for drugs like pembrolizumab or oral medication (pills) for others like olaparib or enzalutamide. The exact schedule and number of visits to the clinic would depend on which treatment combination you receive.

Throughout the study, you would have regular appointments for check-ups, blood tests, and scans to monitor your health, how you are responding to the treatment, and to look for any side effects. These assessments help the doctors understand if the treatment is working and if it's safe for you. The duration of your participation would vary, but typically involves a course of treatment cycles followed by ongoing monitoring.

Some parts of this study have already stopped accepting new patients. If you continue with treatment for a long time and your cancer responds very well, you might even have the option to receive further treatment infusions later on if your cancer were to show signs of returning after stopping the first course. The research team will explain the full details of what's involved, including the total expected time commitment and follow-up plan for your specific situation.