TITLE:
Estimation of PSA Half-Life Following Salvage Radiation Therapy
AUTHORS:
Ajay B. Patel, Katherine S. Tzou, Michael G. Heckman, Colleen S. Thomas, Richard J. Lee, Nitesh Paryani, Thomas M. Pisansky, Jennifer L. Peterson, Robert C. Miller, Stephen J. Ko, Laura A. Vallow, Steven J. Buskirk
KEYWORDS:
Prostate, Salvage, PSA, PSA Kinetics
JOURNAL NAME:
Journal of Cancer Therapy,
Vol.9 No.1,
January
5,
2018
ABSTRACT: Background:We aim to estimate prostate-specific antigen (PSA) half-life after
salvage radiation therapy (SRT) in patients with detectable PSA after radical
prostatectomy (RP). Methods: A total
of 272 patients treated with salvage radiotherapy between July 1987 and July 2010
were included in this IRB approved retrospective analysis. The median pre-salvage radiotherapy
dose was 0.6 ng/mL (range, 0.2 - 21.9 ng/mL), 47 patients had at least a minimum
tumor stage of T3b, 29 had a Gleason score over 7, and median dose was 66.6 Gy
(range, 54.0 - 72.4 Gy). Results: The
estimated PSA half-life in our cohort of
patients was 3.0 months (95% CI, 2.9 - 3.2 months; range, 0.5 - 28.5 months). There was no evidence of a statistically significant association between
PSA half-life and any baseline clinicopathologic characteristics. The
median interval between individual PSA measurements was noted to be 4.6 months
(range, 0.1 - 20.4 months). The median interval from the start of radiation therapy
to the nadir PSA was 6.3 months (range, 1.3 - 79.1
months). PSA half-life remained approximately 3.0 months when accounting for
infrequent and outlier PSA values. Conclusion: The PSA half-life after definitive RT has been reported to be
approximately 1.6 months. Our analysis found the PSA half-life after SRT to be
approximately twice that of patients treated with definitive RT. These
results provide useful information to radiation oncologists when counseling
patients both before and after SRT regarding expectations about PSA measurements.