Shifting the curve: Long-term data redefines survival in metastatic prostate cancer

New long-term data being unveiled at the American Society of Clinical Oncology (ASCO) congress is set to reshape survival outcomes in metastatic hormone-sensitive prostate cancer (mHSPC). Two studies, the global ARCHES trial and the Australian-led ENZAMET trial, highlight the sustained clinical benefits of Astellas’ Xtandi (enzalutamide) in combination with hormone therapy.

The five-year follow-up from Astellas’ Phase 3 ARCHES study shows a significant 30% reduction in the risk of death when Xtandi is combined with androgen deprivation therapy (ADT), compared to ADT alone. Across patient subgroups with both high and low disease burden, two-thirds of men remained alive at five years, a 13% absolute and 30% relative improvement over standard hormonal therapy.

“These findings signal a meaningful step forward in improving outcomes for men facing the disease,” said Naseem Ali, Medical Affairs Lead, Astellas Australia. “Prostate cancer is currently the most diagnosed cancer in Australia and continues to be a major health burden. The growing body of evidence continues to inform the use of enzalutamide in advanced prostate cancer, supporting its role in improving outcomes for some patients.”

Also presented at ASCO are eight-year survival results from the ENZAMET study, an investigator-initiated international Phase 3 trial led by the Australian and New Zealand Urogenital and Prostate Cancer Trials Group (ANZUP) and sponsored by the University of Sydney. ENZAMET compared Xtandi to older non-steroidal anti-androgens (NSAAs), both in combination with testosterone suppression, with or without docetaxel.

The results are compelling: the proportion of patients alive at eight years increased from 40% to 50% with Xtandi. Median overall survival (OS) reached eight years for those on Xtandi versus 5.8 years in the comparator arm.

Professor Christopher Sweeney, Director of the South Australian immunoGENomics Cancer Institute at the University of Adelaide, and Professor Ian Davis, Head of Eastern Health Clinical School and Chair of ANZUP, have been instrumental in steering the ENZAMET study.

“The ANZUP-led ENZAMET trial was the first to show that survival could be improved by addition of enzalutamide to testosterone suppression for people with metastatic hormone sensitive prostate cancer. Now we are able to show that this benefit persists out to more than eight years,” said Professor Davis.

“People with mHSPC have better outcomes if the PSA test becomes undetectable with treatment. ENZAMET has also shown that this is more likely to happen if people are treated with enzalutamide,” he added.

“This means, in 2025, we can now counsel people that they have a 50% chance that they’ll be alive at eight years with the new therapies that we have for metastatic hormone sensitive prostate cancer, compared to 40% who received older types of treatment,” said Professor Sweeney.

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