Low and high-dose-rate brachytherapy in combination with external beam radiotherapy for high risk prostate cancer

Background. Prostate cancer (PCa) in the Russian Federation takes the leading place in the prevalence of cancer among the male population. Objective: to investigate the effect of increasing a single focal dose in high-dose-rate brachytherapy (HDR-BT) in combination with external beam radiotherapy on biochemical failure-free survival and local control in patients with high-risk PCa. Materials and methods. The study included 350 men with PCa in the group of high and extremely high risk of progression. All patients included in the study were divided into 4 groups. Groups 1, 2 and 3 included 276 patients who received HDR-BT with a Ir-192 source with a single dose per fraction: 10 Gy (n = 83), 12 Gy (n = 46) and 15 Gy (n = 147). Group 4 included 74 patients who received low-dose-rate brachytherapy with I-125 sources up to a total focal dose of 110 Gy. At the 2 stage, external beam radiotherapy was a conventional fractionation (single dose of 2 Gy, total - 44-46 Gy). Results. Of 350 patients over a 5-year follow-up period, PCa recurrence was noted in 65 (18.6 %). The 3- and 5-year biochemical failure-free survival rates in the general cohort of patients were 87.4 and 81.4 %. 5-year biochemical failure-free survival was significantly higher in group 3 relative to group 4 and amounted to 89.8 and 74.2 % (p = 0.03). Increasing the dose for HDR-BT from 10 to 12 Gy per fraction significantly reduced the frequency of local relapses from 15.7 % (in group 1) to 2.2 % (in group 2) (p = 0.0001) while maintaining the level of genitourinary and gastrointestinal toxicity. Conclusion. The use of a combination of brachytherapy and external beam radiotherapy in patients with high risk PCa is highly effective in achieving local control of the tumor. The optimal fractionation regime for HDR-BT remains a matter of debate. The use of 15 Gy per fraction for HDR-BT in combination with external beam radiotherapy is the most optimal fractionation regimen in patients with high-risk PCa.