PSA kinetics and PSA bounce following permanent seed prostate brachytherapy

Area of Science:

• Urology
• Radiation Oncology

Background:

• Prostate-specific antigen (PSA) bounce is a transient increase in PSA levels observed after radiation therapy for prostate cancer.
• Understanding PSA bounce is crucial for accurate interpretation of treatment response and avoiding misdiagnosis of recurrence.

Purpose of the Study:

• To determine the incidence, timing, and magnitude of benign PSA bounce following Iodine-125 (125I) prostate brachytherapy.
• To identify clinical and dosimetric factors associated with PSA bounce.
• To differentiate PSA bounce from biochemical failure after 125I prostate brachytherapy.

Main Methods:

• Analysis of 292 men treated with 125I prostate brachytherapy between March 1999 and August 2003 with over 30 months of PSA follow-up.
• PSA bounce defined as an increase >=0.2 ng/ml with spontaneous return to baseline.
• Preplanned implants using transrectal ultrasound (TRUS) with TRUS/fluoroscopy guidance.

Main Results:

• A PSA bounce was observed in 40% of patients.
• Median onset of bounce was 15 months, with a median magnitude of 0.76 ng/ml.
• 15% of patients experienced a bounce magnitude greater than 2 ng/ml. Younger age was the only significant predictor in multivariate analysis.

Conclusions:

• Benign PSA bounces are frequent after 125I prostate brachytherapy, particularly in younger men.
• The magnitude of PSA increase does not reliably distinguish bounce from failure.
• Interpreting early PSA increases requires caution, especially within the first 30 months post-treatment.