The purpose of this study is to learn about how long apalutamide and enzalutamide are taken by men to treat mCSPC.

Prostate cancer is one of the most common cancers in men. The prostate is a gland in the male body that helps make semen. Metastatic cancer is a cancer that has spread to other parts of the body. Castration-sensitive prostate cancer means the cancer is being controlled by keeping the testosterone levels as low as would be expected if the testicles were removed by surgery.

This is a real-world study, not a clinical study. This means that researchers will look at what happens when men receive the treatments prescribed by their own doctor as part of their usual healthcare treatment. In this study, researchers will use information from cancer clinics (Flatiron Health electronic health records).

The study will include patients' information from the database for men who:

• Were identified to have mCSPC.
• Started treatment with apalutamide or enzalutamide (index date) for mCSPC.
• Were 18 years of age or older on the index date. Men in this study will be taking apalutamide or enzalutamide for treatment of their mCSPC. The study will compare how long men take apalutamide or enzalutamide. This study will use patient information from cancer clinics. Information from start of apalutamide or enzalutamide treatment until information is available in the database will be used to describe how long patients receive treatment.

Inclusion Criteria:

• Male patients diagnosed with metastatic prostate cancer
• Initiated apalutamide or enzalutamide for the first-line treatment of metastatic castration-sensitive prostate cancer (mCSPC). Initiation date of first treatment defines the index date.
• Index date on or after 1 January 2020
• Evidence of androgen deprivation therapy (ADT) use between 90 days prior to the index date and 6 months following the index date
• Age ≥18 years on the index date -≥6 months of clinical activity following the index date, unless the patient died

Exclusion Criteria:

• Evidence of castration-resistance prior to the index date
• Received chemotherapy, androgen receptor pathway inhibitor, radiopharmaceuticals, immunotherapy, PARP inhibitor, or estrogens prior to the index date
• Evidence of ADT use between 1 year and 91 days prior to the index date
• Had a prior history of other cancers

Male

Men with metastatic castration-sensitive prostate cancer who initiated apalutamide or enzalutamide and met eligibility criteria will be included in the study. Patients will be identified from the Flatiron Health electronic health records database.

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.