Plain language review: the safety of relugolix combination therapy for advanced prostate cancer

Advanced prostate cancer is a cancer that began in the prostate (a part of the male body) and has spread to other parts of the body. This is a review of two clinical research studies of patients with advanced prostate cancer who were treated with relugolix combination therapy. Relugolix is a medicine taken by mouth that lowers a male sex hormone, called testosterone. Relugolix is sometimes combined with other medicines such as novel hormonal therapies (NHTs) or chemotherapy to treat advanced prostate cancer. In one study, patients were treated with relugolix combined with an NHT (abiraterone or apalutamide). In a second study, patients were treated with relugolix combined with an NHT (enzalutamide) or chemotherapy (docetaxel). Researchers wanted to understand what possible side effects may happen due to taking these medicines together as prescribed. They also wanted to see if relugolix combination therapy worked to lower testosterone in the same way as relugolix taken alone.

Researchers found that most of the side effects of relugolix combined with an NHT or chemotherapy were mild or moderate. Side effects of relugolix combination therapy were similar to the side effects of the medicines when taken alone. However, patients who received relugolix with enzalutamide or docetaxel were more likely to have a serious side effect compared with patients who received relugolix taken alone. Testosterone stayed below 50 nanograms per deciliter (known as castration levels) for patients who received relugolix with NHT or chemotherapy.

Patients who receive relugolix combination therapy generally experience mild or moderate side effects, rather than serious side effects. No new safety issues were found during these studies. Patients maintained low testosterone levels. Patients and their doctors should discuss the benefits and possible harms of relugolix combination therapy to treat advanced prostate cancer.