Comparing the survival outcomes of pembrolizumab with or without enzalutamide in men with previously untreated metastatic castration-resistant prostate cancer.

This study compared the survival and safety outcomes of pembrolizumab (Keytruda; PEM) plus enzalutamide (Xtandi; ENZ) combination versus pembrolizumab alone in patients with previously untreated metastatic castration-resistant prostate cancer (mCRPC). The data showed that PEM plus ENZ combination was associated with increased survival benefits and manageable side effects compared with PEM alone.

Metastatic castration-resistant prostate cancer (mCRPC) is an aggressive form of prostate cancer that has spread beyond the prostate gland and is no longer responsive to hormonal therapy such as androgen deprivation therapy (ADT). ADT reduces the production of androgens (male sex hormones such as testosterone). Reducing these androgens prevents cancer cell growth. Men with mCRPC usually have high levels of prostate-specific antigen (PSA). PSA is a protein made by the cells of the prostate gland. It is used as a marker of cancer progression when it rises after treatment.

Some cancer cells have on their surface proteins, such as PD-L1 that binds to the PD-1 protein on immune cells. This helps cancer cells avoid detection from the immune system. PEM is an immunotherapy that targets the PD-1 protein and helps the immune system detect and find cancer cells. ENZ is an anti-androgen medication. It blocks testosterone from reaching PC cells. It is also used for the treatment of mCRPC. PEM plus ENZ combination has been suggested as an option for treating mCRPC. However, the safety and effectiveness of this combination in men with mCRPC with PD-L1 positive cancer cells are still unknown. 

This study involved 206 men with previously untreated mCRPC. All patients tested positive for the PD-L1 protein. 100 patients were treated with PEM plus ENZ combination, and 106 patients were treated with PEM alone. The average follow-up was 34 months.

Overall, 66% of men in the PEM+ENZ group responded to treatment compared to 56% in the PEM group. The average overall survival (OS) was 25.1 months in the PEM plus ENZ group compared to 18.3 months in the PEM alone group. The addition of ENZ to PEM was associated with a 44% lower risk of death compared to PEM alone.

The average survival without progression or cancer worsening was 6.1 months in the PEM plus ENZ group compared to 4.9 months in the PEM alone group. Patients treated with PEM plus ENZ were 45% less likely to have progression or worsening of cancer than patients treated with PEM alone.

72% of the PEM and ENZ group experienced severe side effects compared to 45.3% in the PEM alone group. The most common side effects were fatigue, muscle and bone-related side effects.

This study concluded that PEM plus ENZ combination increased the survival benefits with manageable side effects compared with PEM alone for the treatment of patients with previously untreated mCRPC positive for PD-L1.

This study looked back in time in medical records data. Information might have been missing. The patients were not randomized to each treatment. This might have influenced the results.