An international study led by Fox Chase Cancer Center radiation oncologist Mark K. Buyyounouski, M.D., M.S. says that men whose prostate specific antigen (PSA) levels rise within 18 months of radiotherapy are more likely to die of their disease. The study is being presented today at the annual meeting of the American Society for Radiation Oncology (ASTRO).
"PSA is the gold standard for following prostate cancer patients after they receive radiation or surgery. But we haven't know if having PSA rise sooner means a patient has a greater danger of dying of prostate cancer, though it seems logical," Buyyounouski says.
Using a single institution database, Buyyounouski and colleagues showed previously that men who suffered an early biochemical failure, which is defined as their 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 in the clinic.
"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," says Buyyounouski.
A total of 2,132 men with clinically localized prostate cancer who suffered biochemical failure after treatment were studied. The median interval between treatment and biochemical failure was 35.2 months for the entire study group. However, 19% of patients developed biochemical failure at 18 months or less. The five-year cancer-specific survival for these men was 69.5% compared with 89.8% 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 Gleason score, tumor stage, age, and PSA doubling time. However, the interval to biochemical failure had the best predictive value for cancer-specific mortality, compared with the other variables. Currently, most physicians do not start treatment based on biochemical failure alone, but rather wait until the PSA reaches a high level or there is some other evidence tumor spread. "The potential impact of this finding is that patients can initiate treatment far sooner without waiting for other signs or symptoms of prostate cancer," Buyyounouski says. "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."