Increasing Fractional Doses Increases the Probability of Benign PSA Bounce in Patients Undergoing Definitive HDR Brachytherapy for Prostate Cancer

Publication date: Available online 16 January 2017
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Carlin R. Hauck, Hong Ye, Peter Y. Chen, Gary S. Gustafson, Amy Limbacher, Daniel J. Krauss
PurposeProstate-specific antigen (PSA) bounce is a temporary elevation of PSA above a prior nadir. The purpose of this study was to determine if the frequency of a PSA bounce following high dose rate (HDR) interstitial brachytherapy for the treatment of prostate cancer is associated with individual treatment fraction size.Materials and MethodsBetween 1999 and 2014, 554 patients were treated for low or intermediate-risk prostate cancer with definitive HDR brachytherapy as monotherapy and had at least 3 subsequent PSA measurements. Four different fraction sizes were used: 950 cGy x 4, 1200 cGy x 2, 1350 cGy x2, 1900 cGy x 1. Four definitions of PSA bounce were applied: ≥0.2, ≥0.5, ≥1.0, and ≥2.0 ng/mL above prior nadir with subsequent return to nadir.ResultsMedian follow-up was 3.7 years. The actuarial 3-year rate of PSA bounce for the entire cohort was 41.3%, 28.4%, 17.4%, and 6.8% for nadir +0.2, +0.5, +1.0, and +2.0 ng/mL, respectively. The 3-year rate of PSA bounce >0.2 ng/mL was 42.2%, 32.1%, 41.0% and 59.1% for the 950, 1200, 1350 and 1900 cGy per fraction levels respectively (p=0.002). The hazard ratio for bounce >0.2 ng/ml for patients receiving a single fraction of 1900 cGy compared to those receiving treatment in multiple fractions was 1.786 (p=0.024). For patients treated with a single 1900 cGy fraction, the 1-, 2-, and 3-year rates of PSA bounce exceeding the Phoenix biochemical failure definition ("nadir + 2"), were 4.5%, 18.7%, and 18.7%, higher than the rates for all other administered dose levels (p=0.025).ConclusionsThe incidence of PSA bounce increases with single-fraction HDR treatment. Knowledge of post-treatment PSA kinetics may aid in decision making regarding management of potential biochemical failures.

Teaser

Following definitive radiation therapy for prostate cancer, benign elevations of prostate serum antigen (PSA), known as bounces, can complicate interpretation of post-treatment PSA values. We reviewed 554 patients treated at a single institution with HDR brachytherapy as monotherapy for the definitive treatment of prostate cancer, and analyzed their post-treatment PSA trends. Patients treated with a high single-fraction dose had a higher rate of experiencing post-treatment PSA bounce, than those treated with lower fractional doses.


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