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Highlights of the American Society of Clinical Oncology – Genitourinary Cancers Symposium 2023

Clinicians and researchers gathered last month at the American Society of Clinical Oncology Genitourinary Cancers Symposium (ASCO GU) in San Francisco. Hundreds of presentations covered advances in screening, diagnosis, treatment, monitoring, and survivorship in prostate and other GU cancers. Below is a sampling of some of the important findings. You can read more research summaries on UroToday.

Localized Prostate Cancer

A plant-based diet lowers the risk of prostate cancer getting worse or coming back

In a study of more than 2000 men with localized prostate cancer, patients completed a questionnaire about their diet and were followed for, on average, more than 7 years. Researchers gave each person an “overall plant-based” diet index score and a “healthy plant-based” diet score. Men with the highest overall plant-based diet score had a 52% lower risk of prostate cancer progression and a 53% lower risk of disease recurrence, compared to men with the lowest plant-based diet score. Even more striking was the benefit of a healthy plant-based diet in older men: among men over age 65, consuming a healthy plant-based diet was linked to a nearly 60% reduction in prostate cancer recurrence.

Urinary, bowel, and sexual function effects of surgery vs. stereotactic body radiation therapy

This study is the first “gold standard” evidence (i.e., randomized phase 3 trial) comparing side effects of surgery vs. five sessions of radiation therapy (stereotactic body radiation therapy, SBRT). Patients with localized prostate cancer were randomized to one of these two treatments and reported on their functioning two years later. More surgery patients reported using urinary pads compared to SBRT patients. However, there was no difference in urinary function as reported on questionnaires by patients or clinicians. SBRT patients reported worse bowel problems, but better sexual function. Patients and doctors may consider this information when deciding among treatments.

Advanced Prostate Cancer

Triplet therapy in metastatic hormone-sensitive prostate cancer is beneficial regardless of volume or risk of disease

In 2022, the combination of darolutamide + docetaxel + hormone therapy was FDA-approved for metastatic hormone-sensitive prostate cancer (mHSPC). All mHSPC is not the same, and it is important to know how well this combination works in different subtypes of disease. High-volume disease is defined by the number and location of metastases. High-risk disease can be defined by Gleason score as well as by the number and location of metastases.

Researchers analyzed data from over 1300 patients in the large ARASENS clinical trial. Darolutamide + docetaxel + hormone therapy prolonged life compared to placebo + docetaxel + hormone therapy in both high- and low-volume disease and in both high- and low-risk disease. For example, among patients with high-volume disease, patients receiving darolutamide were 31% less likely to die vs. patients receiving placebo. Similarly, among patients with low-volume disease, darolutamide was associated with 32% lower risk of death.

These data further support the use of treatment intensification in mHSPC regardless of certain disease characteristics. Hormone therapy alone is no longer the standard of care. Read more here.

Clinical trials show benefit of PARP inhibitors in combination treatment for metastatic castration-resistant prostate cancer, regardless of gene mutation status

Olaparib and rucaparib are drugs called PARP inhibitors that are currently FDA-approved for patients with mCRPC who have progressed on other treatments and have mutations in certain genes that are involved in DNA repair (such as BRCA). Now, two large randomized clinical trials show benefit of PARP inhibitors in combination with novel hormonal therapy.

These trials differ from the current approvals in two important ways: 1) Patients were not required to have specific gene mutations to enter the trial and 2) The drugs were given as “first line” treatment for mCRPC, meaning that these were the first life-prolonging treatments patients received once they were determined to have reached the castration-resistant disease stage of prostate cancer (they did receive therapy at earlier stages of prostate cancer).

 These results may ultimately lead to adoption of new combination treatment approaches to mCRPC, specifically, broader use of PARP inhibitors.

  • Talazoparib + enzalutamide reduces risk of disease progression

In the TALAPRO-2 trial, talazoparib, another PARP inhibitor (not yet FDA-approved for prostate cancer), was tested in combination with enzalutamide in more than 800 patients. The results showed that patients treated with talazoparib + enzalutamide were 37% less likely to have disease progression on imaging, compared to patients treated with placebo + enzalutamide. The effect was greater in patients with specific gene mutations: combination treatment was associated with a 54% lower risk of progression. Other study measures (such as PSA dropping by 50% and use of other therapies) also favored the combination of talazoparib + enzalutamide. More patients treated with the combination experienced moderate-to-serious adverse events.

  • Final trial results: olaparib + abiraterone associated with longer overall survival

PROpel is a randomized trial of nearly 800 patients with mCRPC comparing abiraterone + olaparib to abiraterone + placebo. The trial data has now “matured,” meaning that the results of median overall survival are final. Investigators reported that patients treated with the combination were 19% less likely to die. Median survival time was 42.1 months on combination treatment ­­vs. 34.7 months for abiraterone + placebo. The greatest benefit was seen in patients with mutations in BRCA genes.

Impact of intermittent vs. continuous hormone therapy on the heart, bones, blood sugar, and other health events

Patients with metastatic prostate cancer may require hormone therapy for months to years. There is mixed evidence on the health effects of continuous hormone therapy vs. intermittent use (i.e., with gaps in treatment). Researchers reviewed health records of more than 2200 patients with metastatic prostate cancer; nearly 500 received intermittent hormone therapy and over 1700 received continuous therapy. Patients were followed for 1-2 years.

Patients receiving continuous hormone therapy had a 42% higher risk of major cardiovascular events such as heart attack, stroke, blood clots in the lungs, or death from any cause. However, there was no significant difference in deaths caused only by cardiovascular disease. There was also no difference between the two treatment groups in risk of other, non-cardiovascular complications (a combined measure of diabetes, high cholesterol, fractures, and osteoporosis).

This study provides additional information on the risks of different hormone therapy schedules as patients and their doctors consider how best to use this treatment.

Becky Campbell
Becky Campbell develops medical content at the Prostate Cancer Foundation. She has previously worked in outcomes research and in science education.