Comparison of salvage high dose-rate brachytherapy and external beam radiotherapy for treatment of prostate cancer local recurrence after radical prostatectomy

Aim. To compare clinical efficacy of salvage high dose-rate brachytherapy (HDR-BT) and external beam radiotherapy (EBR) in treatment of local recurrence of prostate cancer after radical prostatectomy (RP).
Materials and methods. Between January 2017 and December 2020, 60 patients with local recurrence of prostate cancer after RP were treated at the Russian Scientific Center of Roentgenology and Radiology. Two groups were identified: group 1 included 30 patients who underwent salvage external beam radiation therapy (EBRT) according to the classical fractionation regimen; in group 2, within the framework of the scientific protocol, 30 patients underwent 2 fractions of salvage HDR-BT with single boost dose of 15 Gy for total boost dose of 30 Gy. All patients in group 2 underwent pelvic multiparametric magnetic resonance imaging and positron emission tomography-computed tomography with prostatespecific membrane antigen ligands. In the 2nd group, transrectal biopsy of the prostate bed was also performed. Overall and biochemical recurrence-free survival, as well as the profile of early and late radiation complications, were analyzed.
Results. Mean age of the patients at the time of salvage radiation therapy was 67.5 years (95 % confidence interval 66.1–69). Median time before development of biochemical relapse after RP was 24 months (interquartile range 13–46 months). Median follow-up period for all patients was 45 months (interquartile range 36–63 months). There were no dropouts in this study. The overall survival rate was 100 % in both groups. Comparative analysis of prostate specific antigen (PSA)-specific recurrence-free survival showed a clear trend toward an increase in the brachytherapy group; however, with the number of observations, statistically significant differences could not be achieved (p = 0.075). Salvage EBRT is more toxic than salvage HDR-BT. Comparative assessment of radiation adverse effects revealed higher frequency of early genitourinary toxicity of grade I and intestinal toxicity of grades I and II in the salvage EBRT group than in the salvage brachytherapy group, as well as late gastrointestinal toxicity of grade I and II.
Conclusion. Salvage HDR-BT with 15 Gy × 2 fractions with total boost dose of up to 30 Gy was proved to be a promising treatment for local recurrence of prostate cancer after RP with an acceptable toxicity profile. There was also a trend towards increased PSA-specific recurrence-free survival in the salvage brachytherapy group compared with the salvage EBRT group.

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