PHILADELPHIAA temporary increase or "bounce" in the PSA level following radiotherapy of prostate cancer is a common occurrence and does not necessarily indicate increased risk that cancer will recur, according to a presentation at the American Society for Therapeutic Radiation and Oncology 48th Annual Meeting (abstract 1129). This ob-servation affects clinical practice for both radiation oncologists and urologists, said Eric Horwitz, MD, of Fox Chase Cancer Center. He urged clinicians to consider additional PSA tests in patients who have had a PSA rise following radiotherapy to determine whether the PSA level returns to normal before recommending further treatment.
The study was based on two pooled multi-institutional data sets comprising more than 7,500 prostate cancer patients treated with either external-beam radiotherapy or brachytherapy from the late 1980s to the mid-1990s. The study excluded patients who received neoadjuvant androgen ablation. A total of 4,839 patients received at least 60 Gy external-beam irradiation. The remaining 2,693 had permanent implants with either I-125 (68%) or Pd-103 (32%).
A PSA bounce was defined as an increase of at least 0.2 ng/mL over an earlier level, followed by a decline. About 18% of patients experienced at least one PSA bounce during the 3 years following radiation therapy. Rates were comparable with external-beam radiation and brachytherapy, but the incidence was somewhat higher with I-125 than with Pd-103 implants. Men less than 70 years of age were more likely to exhibit a bounce than older men. In those who received external-beam irradiation, a higher pretreatment PSA and a more advanced T stage were each associated with greater likelihood of a bounce.
Long-term outcomes were determined in patients who had remained free of disease 3 years after their initial treatment. Median follow-up was 6 years for the external-beam radiation patients and 5 years 3 months for the brachytherapy patients. No difference in any disease outcome was evident between patients with or without a PSA bounce at 10 years.
Among patients who received external-beam radiation, 55% of patients who had a PSA bounce and 53% with no bounce were free of biochemical evidence of disease at 10 years. Among the brachytherapy patients, 10-year rates of biochemical disease-free survival were 62% (bounce) and 72% (no bounce). Whether patients experienced a bounce had no effect on distant metastases, cause-specific survival, or overall survival.