Abstract
BACKGROUND: Long-term data on the efficacy of robotic stereotactic body radiotherapy (SBRT) for localized prostate cancer (LPC) remain limited. This study aimed to evaluate the 10-year treatment outcomes of SBRT in LPC patients and identify key prognostic factors. METHODS: A total of 82 patients with LPC who underwent five-fraction SBRT (doses of 35-37.5 Gy) were included. The median follow-up duration was 11.0 years (range, 3.3-15.9 years). Clinical outcomes, including the biochemical failure-free survival (BCFFS), clinical failure-free survival (CFFS), and prostate-specific antigen (PSA) kinetics, were analyzed to evaluate the impact of various clinical and treatment factors on prognosis. RESULTS: The 10-year BCFFS and CFFS rates were 86.3% (95% confidence interval [CI], 78.6-94.8) and 86.7% (95% CI, 78.8-95.4), respectively. Nine cases of biochemical failure were observed, alongside local (n = 1), regional (n = 2), and distant (n = 5) metastases. The cancer-specific survival rate was 100%. The median PSA nadir was 0.09 ng/ml (range, 0.0-3.12 ng/ml) and the median interval to PSA nadir was 52.8 months (range, 0.4-170.2 months). There was a negative correlation between the time to the PSA nadir and the PSA nadir value (r = -0.233, p = 0.035). Daily SBRT was associated with improved BCFFS compared to every-other-day treatment (hazard ratio [HR], 0.220; 95% CI, 0.067-0.720; p = 0.012), while a longer interval to PSA nadir (≥ 5 years) was associated with better CFFS (HR, 0.120; 95% CI, 0.015-0.944; p = 0.044). CONCLUSIONS: Robotic SBRT for LPC demonstrates durable long-term efficacy. Daily treatment schedules and interval to PSA nadir were identified as crucial prognostic indicators. These findings highlight the importance of PSA kinetics in predicting treatment success following robotic SBRT.