Kinetics differences between PSA bounce and biochemical failure in patients treated with 125I prostate brachytherapy

To determine the helpful factors to distinguish prostate-specific antigen failure from prostate-specific antigen bounce with large magnitude.

From October 2004 to December 2009, 242 patients with prostate cancer treated with (125)I brachytherapy were analyzed, 88 patients were excluded because the follow-up durations were shorter than 5 years. Their median follow-up was 80.4 months (60.0-123.9). Prostate-specific antigen failure was determined using the Phoenix definition. Prostate-specific antigen bounce was defined as an increase ≥0.2 ng/ml above the nadir, followed by a spontaneous return to the nadir. Prostate-specific antigen bounce +2 was defined as a prostate-specific antigen rise by 2.0 ng/ml or more above the nadir.

The 5-year biochemical relapse-free survival rate was 90.2%. Prostate-specific antigen failure and prostate-specific antigen bounce +2 were seen in 23 patients (14.9%) and 12 patients (7.8%), respectively. On univariate analysis, age at implant (P = 0.028), T stage (P = 0.020), time to prostate-specific antigen failure or prostate-specific antigen bounce (time to onset) (P = 0.0008), prostate-specific antigen velocity (P = 0.0003) and prostate-specific antigen doubling time (P = 0.0004) were significant for the distinction between prostate-specific antigen failure and prostate-specific antigen bounce +2. On multivariate analysis, no factor was the statistically significant factor. On receiver operating characteristic curve analysis, time to onset with a cutoff value of 29.8 months, prostate-specific antigen velocity of 0.18 ng/ml/month and prostate-specific antigen doubling time of 6.3 months had the highest accuracy of 82.9, 82.9 and 82.9% for prostate-specific antigen failure, respectively.

Time to onset, prostate-specific antigen velocity and prostate-specific antigen doubling time would be helpful for distinction between prostate-specific antigen failure and prostate-specific antigen bounce +2.