PSA after incidental irradiation of the nonmalignant prostate: long-term changes

Incidental irradiation of the prostate may affect serum prostate-specific antigen (PSA). However, scarce data exist on PSA changes after irradiation of noncancerous prostatic tissue. This is an update of a study on PSA after pelvic irradiation.

From 1997 to 2007, blood samples of 33 men were examined who had undergone pelvic irradiation for rectal or anal cancer. The planning target volume included the prostate in all cases. No patient had clinical evidence of prostatic disease. Radiotherapy was applied in fractions of 1.8-2 Gy up to 40-50 Gy (n = 3), 50-60 Gy (n = 21), and 60-65 Gy (n = 2). Seven patients received 5 x 5 Gy. Serum PSA was measured before, during, and after radiotherapy periodically. Median log (PSA) changes were calculated according to elapsed time from starting radiotherapy. The significance was tested with chi(2)-test.

18 patients died during follow-up. For 15 patients, long-term PSA data with a median follow-up of 9 years (2,546-3,528 days) are available. PSA levels rose during the first weeks of irradiation peaking at 2-4 weeks with a significant 2.7-fold increase (p < 0.01). 1 year after radiation therapy, PSA declined below (90%) the preirradiation level, but this difference was not significant (p = 0.36). On further follow-up PSA did not change up to 8.9 years after radiotherapy (p = 0.36).

Irradiation of the prostate causes transient increase of serum PSA. By 1 year, PSA has returned near the preirradiation value and stays there for at least 9 years. A major interference with prostate cancer screening or surveillance after radiotherapy is therefore unlikely.