Men whose prostate-specific antigen rise within 18 months of radiotherapy are more likely to have metastases and die of their disease, according to an international study led by Mark K. Buyyounouski, MD, MS, of Fox Chase Cancer Center reported at the ASTRO Annual Meeting.
Previous results from Fox Chase alone by Dr. Buyyounouski and colleagues showed that men who had an early biochemical failure—i.e., the lowest PSA level plus 2 ng/mL—were at greater risk of dying of prostate cancer. The new study confirms those results using a multinational database and shows that the measure is ready for use clinically.
“Now we can use the simple criteria from this study, which is widely available for anyone who has PSA testing, to identify men who have a greater than 25% chance of dying from prostate cancer in the next five years. That is huge. There is nothing else that can do that,” Dr. Buyyounouski said in a news release.
The study included 2,132 men with clinically localized prostate cancer who had biochemical failure after treatment. The median interval between treatment and biochemical failure was 35.2 months overall, but 19% of patients developed biochemical failure by 18 months or sooner. The five-year cancer-specific survival for this group of men was about 70% compared with 90% for men who developed biochemical failure after 18 months.
A multivariate analysis showed that the interval to biochemical failure correlated with cancer-specific survival, as did the Gleason score, tumor stage, age, and PSA doubling time. Of all the variables, though, the one with the best predictive value was the interval to biochemical failure.
Current practice, Dr. Buyyounouski explained, is not to start treatment based on biochemical failure alone but to wait until the PSA reaches a high level or there is some other evidence of metastasis.
“The potential impact of this finding is that patients can initiate treatment far sooner without waiting for other signs or symptoms of prostate cancer,” he said. “If a patient has biochemical failure at 16 months, rather than wait and learn later that the PSA is rising sharply and risk the development of distant metastasis, therapy can be started sooner based on the increased risk of death.”