PSA Bounce and Biochemical Failure After Brachytherapy for Prostate Cancer: A Study of 820 Patients With a Minimum of 3 Years of Follow-Up

Abstract

To determine clinical or dosimetric factors associated with a prostate-specific antigen (PSA) bounce, as well as an association between a PSA bounce and biochemical relapse-free survival (bRFS), in patients treated with iodine-125 brachytherapy. A variety of clinical and treatment factors were examined in 820 patients who had a minimum of 3 years of PSA follow-up with T1-T2cN0M0 prostate cancer. Four different PSA threshold values were used for defining a PSA bounce: a PSA rise of ≥ 0.2, ≥ 0.4, ≥ 0.6, and ≥ 0.8 ng/mL. A PSA bounce of ≥ 0.2, ≥ 0.4, ≥ 0.6, and ≥ 0.8 ng/mL was noted in 247 patients (30.1%), 161 (19.6%), 105 (12.8%), and 78 (9.5%), respectively. The median time to the first PSA rise was 17.4, 16.25, 16.23, and 15.71 months, respectively, vs. 34.35 months for a biochemical failure (p < 0.0001). A PSA rise of ≥ 0.2 ng/mL was the only definition for which there was a significant difference in bRFS between bounce and non-bounce patients. The 5-year bRFS rate of patients having a PSA bounce of ≥0.2 was 97.7% vs. 91% for those who did not have a PSA bounce (p = 0.0011). On univariate analysis for biochemical failure, age, risk group, and PSAs per year had a statistically significant correlation with PSA bounce of ≥ 0.2 ng/mL. On multivariate analysis, age and PSAs per year remained statistically significant (p < 0.0001 and p = 0.0456, respectively). A bounce definition of a rise ≥ 0.2 ng/mL is a reliable definition among several other definitions. The time to first PSA rise is the most valuable factor for distinguishing between a bounce and biochemical failure.