Prostate Int. 2016 Mar;4(1):25-9. doi: 10.1016/j.prnil.2015.12.001. Epub 2015 Dec 12.
Prostate-specific antigen kinetics following hypofractionated stereotactic body radiotherapy boost as post-external beam radiotherapy versus conventionally fractionated external beam radiotherapy for localized prostate cancer.
Prostate international
Jeong Hoon Phak, Hun Jung Kim, Woo Chul Kim
Affiliations
Affiliations
- Department of Radiation Oncology, Inha University Hospital, Inha University of Medicine, Inchon, South Korea.
PMID: 27014661
PMCID: PMC4789329 DOI: 10.1016/j.prnil.2015.12.001
Abstract
BACKGROUND: Stereotactic body radiotherapy (SBRT) has emerged as an effective treatment for localized prostate cancer. The purpose of this study was to compare the prostate-specific antigen (PSA) kinetics between conventionally fractionated external beam radiotherapy (CF-EBRT) and SBRT boost after whole pelvis EBRT (WP-EBRT) in localized prostate cancer.
METHODS: A total of 77 patients with localized prostate cancer [T-stage, T1-T3; Gleason score (GS) 5-9; PSA < 20 ng/mL] were enrolled. A total of 35 patients were treated with SBRT boost (21 Gy in 3 fractions) after WP-EBRT and 42 patients were treated with CF-EBRT (45 Gy WP-EBRT and boost of 25.2-30.6 Gy in 1.8-Gy fractions). PSA nadir and rate of change in PSA (slope) were calculated and compared.
RESULTS: With a median follow-up of 52.4 months (range, 14-74 months), the median PSA nadir and slope for SBRT boost were 0.29 ng/mL and -0.506, -0.235, -0.129, and -0.092 ng/mL/mo, respectively, for durations of 1 year, 2 years, 3 years, and 4 years postradiotherapy. Similarly, for CF-EBRT, the median PSA nadir and slopes were 0.39 ng/mL and -0.720 ng/mL/mo, -0.204 ng/mL/mo, -0.121 ng/mL/mo, and -0.067 ng/mL/mo, respectively. The slope of CF-EBRT was significantly different with a greater median rate of change for 1 year postradiotherapy than that of SBRT boost (P = 0.018). Contrastively, the slopes of SBRT boost for durations of 2 years, 3 years, and 4 years tended to be continuously greater than that of CF-EBRT. The significantly lower PSA nadir was observed in SBRT boost (median nadir 0.29 ng/mL) compared with CF-EBRT (median nadir 0.35 ng/mL, P = 0.025). Five-year biochemical failure (BCF) free survival was 94.3% for SBRT boost and 78.6% for CF-EBRT (P = 0.012).
CONCLUSION: Patients treated with SBRT boost after WP-EBRT experienced a lower PSA nadir and there tended to be a continuously greater rate of decline of PSA for durations of 2 years, 3 years, and 4 years than with CF-EBRT. The improved PSA kinetics of SBRT boost over CF-EBRT led to favorable BCF free survival.
Keywords: Cyberknife; PSA kinetics; PSA nadir; Prostate cancer; Stereotactic body radiotherapy
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