HYPOFRACTIONATED STEREOTACTIC RADIOTHERAPY (SBRT) FOR RECURRENT OLIGOMETASTATIC PROSTATE CANCER: A METHANALYSIS

Objective: To evaluate the efficacy of SBRT in oligometastatic recurrent prostate cancer (CaP), aiming to study the existence of any relationship between biological effective dose (BED) and local control (LC). Conclusion: The local control rate with SBRT was excellent with very low acute and late severe toxicity rates. Our data suggest that there is a dose relationship between BED and LC, with BED> 100Gy3 producing better LC rates. Methodology and materials: A search for eligible studies in the Medline, Embase, the Cochrane Library databases, and area conference proceedings were conducted until May 2019. A metaanalysis estimating LC rates, progression-free survival (PFS), androgen deprivation-free survival (AD-FS), acute and late toxicities were estimated. A meta-regression to assess whether there is a relationship between BED and LC was conducted. In the univariate analysis, the studies were separated by study design, number of metastatic sites, metastatic sites, radiotherapy machine used and PSA level at the time of SBRT. A p value <0.05 was considered significant. Results: Twenty-three observational studies with a total of 1441 treated lesions were included in the meta-analysis. The ratio of LC, PFS and AD-FS ratio was 0.976 (95% CI 0.96 – 0.98), 0.413 (CI 0.378-0.477), and 20.1 months (95% CI 14.5 – 25.6). In meta-regression, a linear relationship between BED and LC was detected (p = 0.017). Stratifying the BED into 3 levels (BED <100 Gy3, BED 100-130 Gy3 and BED> 130Gy3) a significant difference was observed between BED <100 Gy3 (LC = 88%) vs BED> 100Gy3 (LC = 96%). The rate of any combined acute or late toxicity (gastrointestinal + genitourinary) ≥ grade 2 was 1.3% and 1.2% respectively.