A Phase 3 clinical trial led by UC San Francisco researchers discovered that combining testosterone-blocking drugs in patients with prostate cancer relapse is better at treating prostate cancer than treatment with a single drug.
Prostate cancer treatment is usually carried out with one of several testosterone-lowering drugs for a set period of time.
However, the new approach can extend the time between debilitating drug treatments without prolonging the time it takes to recover from each treatment.
“This adds to a growing body of evidence in favour of more intensive testosterone-blocking therapy for treating prostate cancer,” said Rahul Aggarwal MD, professor in the UCSF School of Medicine and lead author of the paper.
The research, ‘Open-Label Study of Intensification of Androgen Blockade in Patients With High-Risk Biochemically Relapsed Castration-Sensitive Prostate Cancer,’ was published in the Journal of Clinical Oncology.
A case for intensifying prostate cancer treatment
The new study focused on patients who had surgery for prostate cancer, and yet the cancer relapsed and was detected through a sudden jump in the blood levels of a protein called prostate-specific antigen (PSA).
Aggarwal explained: “We looked at patients who had a fast rise in their PSA – an indicator of a higher-risk form of relapsed prostate cancer.
“Our goal was to test several different hormone therapy strategies to find the best approach in terms of delaying the cancer’s progression.”
Between 2017 and 2022, 503 patients were randomly assigned to take a single testosterone-lowering therapy chosen by their oncologist or to combine it with one or two other testosterone-lowering drugs.
The additional drugs were already FDA-approved for other cancers but hadn’t been tested in this way with prostate cancer.
The patients stayed on the assigned therapy for a year. Whether given singly or in combination, the drugs caused their testosterone to plummet.
That put the brakes on their cancer but also caused fatigue, hot flashes, decreased libido and other problems for patients, according to Aggarwal.
Combining drugs could be the new way forward
Compared to patients who only received a single drug therapy during their year of prostate cancer treatment, patients who received either one or two additional drugs stayed cancer-free, with low PSA levels for longer.
Once off the treatment, patients who took the combination therapies saw their testosterone levels recover just as fast as others who took the single drug.
The researchers are following up with a more detailed analysis of how patients fared when treating prostate cancer – which side effects they experienced and for how long, and how they felt overall as they recovered.
Aggarwal concluded: “New cancer therapies must clear a high bar to make their way to patients.
“With the evidence in this study and others, combination hormone therapy should be considered a standard of care in prostate cancer patients with high-risk relapse after prior treatment.”
