Hypofractionated SBRT versus conventionally fractionated EBRT for prostate cancer: comparison of PSA slope and nadirReport as inadecuate




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Radiation Oncology

, 9:42

Clinical Radiation Oncology

Abstract

BackgroundPatients with early stage prostate cancer have a variety of curative radiotherapy options, including conventionally-fractionated external beam radiotherapy CF-EBRT and hypofractionated stereotactic body radiotherapy SBRT. Although results of CF-EBRT are well known, the use of SBRT for prostate cancer is a more recent development, and long-term follow-up is not yet available. However, rapid post-treatment PSA decline and low PSA nadir have been linked to improved clinical outcomes. The purpose of this study was to compare the PSA kinetics between CF-EBRT and SBRT in newly diagnosed localized prostate cancer.

Materials-methods75 patients with low to low-intermediate risk prostate cancer T1-T2; GS 3 + 3, PSA < 20 or 3 + 4, PSA < 15 treated without hormones with CF-EBRT >70.2 Gy, <76 Gy to the prostate only, were identified from a prospectively collected cohort of patients treated at the University of California, San Francisco 1997–2012. Patients were excluded if they failed therapy by the Phoenix definition or had less than 1 year of follow-up or <3 PSAs. 43 patients who were treated with SBRT to the prostate to 38 Gy in 4 daily fractions also met the same criteria. PSA nadir and rate of change in PSA over time slope were calculated from the completion of RT to 1, 2 and 3 years post-RT.

ResultsThe median PSA nadir and slope for CF-EBRT was 1.00, 0.72 and 0.60 ng-ml and -0.09 -0.04 -0.02 ng-ml-month, respectively, for durations of 1, 2 and 3 years post RT. Similarly, for SBRT, the median PSA nadirs and slopes were 0.70, 0.40, 0.24 ng and -0.09 -0.06 -0.05 ng-ml-month, respectively. The PSA slope for SBRT was greater than CF-EBRT p < 0.05 at 2 and 3 years following RT, although similar during the first year. Similarly, PSA nadir was significantly lower for SBRT when compared to EBRT for years 2 and 3 p < 0.005.

ConclusionPatients treated with SBRT experienced a lower PSA nadir and greater rate of decline in PSA 2 and 3 years following completion of RT than with CF-EBRT, consistent with delivery of a higher bioequivalent dose. Although follow-up for SBRT is limited, the improved PSA kinetics over CF-EBRT are promising for improved biochemical control.

KeywordsSBRT Stereotactic body radiotherapy Prostate External beam Conventionally fractionated Nadir Kinetics Slope AbbreviationsSBRTStereotactic body radiotherapy

CF-EBRTConventionally fractionated external beam radiotherapy.

Electronic supplementary materialThe online version of this article doi:10.1186-1748-717X-9-42 contains supplementary material, which is available to authorized users.

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Author: Mekhail Anwar - Vivian Weinberg - Albert J Chang - I-Chow Hsu - Mack RoachIII - Alexander Gottschalk

Source: https://link.springer.com/







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