The use of relugolix in addition to radiotherapy in patients with prostate cancer

The study investigated the use of relugolix (Relumina), a hormonal therapy drug, in addition to radiotherapy (RT), in managing prostate cancer. The study found that relugolix was effective in reducing androgen (male sex hormones such as testosterone) levels and well tolerated in these patients.

Prostate cancer is the most frequently diagnosed cancer in men. It grows slowly and is more common in older men. It usually grows in response to androgens. Therefore, treatment often involves androgen deprivation therapy (ADT). This is hormonal therapy that reduces androgens. ADT is commonly coupled with external beam radiotherapy (EBRT).

Gonadotropin-releasing hormone (GnRH) receptor antagonists (blockers) are a type of ADT. Degarelix (Firmagon) is a commonly used GnRH blocker is given as an injection. Relugolix is a new GnRH blocker under investigation. It is administered orally (tablet). The safety and effectiveness of relugolix compared to degarelix in addition to EBRT in patients with prostate cancer remain under investigation.

103 patients with prostate cancer were included in the study. They were randomly assigned to 2 groups. The first group (65 patients) received oral relugolix every day for 24 weeks. The second group received degarelix injections under the skin (subcutaneous) every 4 weeks for 24 weeks. All patients also received EBRT. Patients were followed up for 12 weeks after ADT was stopped.

Effective reductions of testosterone levels (below 1.73 nmol/L or 50 ng/dL) were achieved in 95% of patients in group 1 and 89% in group 1. Better reductions of testosterone levels (below 0.7 nmol/L or 20 ng/dL) were achieved by 82% in group 1 and 68% in group 2. 12 weeks into stopping treatment, testosterone levels were recovered in 52% of group 1 and 16% of group 2.

After 12 weeks of treatment, the prostate size was similarly reduced in group 1 (by 26%) and group 2 (by 29%). The prostate-specific antigen (PSA) is a blood marker of prostate cancer. PSA levels decreased by 50% or more in 97% of patients in both groups.

86% of patients in group 1 reported at least one side effect compared to 97% in group 2. Severe side effects were reported in 2% of patients in group 1 and 11% in group 2. The most common side effects were hot flushes (57% in group 1 and 61% in group 1).

This study concluded that relugolix was a safe and effective addition to EBRT in patients with prostate cancer.  

The study used patient questionnaires to assess drug compliance which may not be ideal. Also, the sample size was too small and the follow-up period was too short. This study was funded by Takeda, the manufacturer of relugolix.