Prostate-Specific Antigen Bounce After Permanent Iodine-125 Prostate Brachytherapy—An Australian Analysis

Abstract

To report on prostate-specific antigen (PSA) "bounces" after (125)I prostate brachytherapy to review the relationship to biochemical control and correlate both clinical and dosimetric variables. We analyzed 194 hormone-naive patients with a follow-up of ≥ 3 years. Four bounce definitions were applied: an increase of ≥ 0.2 ng/mL (definition I), ≥ 0.4 ng/mL (definition II), ≥ 15% (definition III), and ≥ 35% (definition IV) of a previous value with spontaneous return to the prebounce level or lower. Using definition I, II, III, and IV, a bounce was detected in 50%, 34%, 11%, and 9% of patients, respectively. The median time to onset was 14-16 months, the duration was 12-21.5 months, and the magnitude of the increase was 0.5-2 ng/mL. A magnitude of >2 ng/mL, fulfilling the criteria for biochemical failure (BF) according to the American Society for Therapeutic Radiology and Oncology Phoenix definition, was detected in 11.3%, 16.9%, 47.6%, and 50% using definitions I, II, III, and IV, respectively; 11 patients (5.7%) had true BF. The PSA bounces occurred earlier than BF (p < 0.001). The prediction of BF remains controversial and is probably unrelated to biochemical control. The only statistically significant factor predictive of a PSA bounce was younger age (definitions I and II). PSA bounces are common after brachytherapy. All definitions resulted in a high number of false-positive calls for BF during the first 2 years. The definition of an increase of ≥ 0.2 ng/mL should be preferred because of the lowest number of false-positive results for BF. Patients experiencing a PSA bounce during the first 2 years after brachytherapy should undergo surveillance every 3-6 months. Additional investigations are recommended for elevated postimplant PSA levels that have not corrected by 3 years of follow-up.