Purpose: Until now, most long-term results for brachytherapy only has been published for low-dose-rate (LDR) seeds. Due to radiobiology reasons, high-dose-rate (HDR) mono-brachytherapy is of growing interest. The aim of the study was to report long-term biochemical control rate and toxicities with HDR monotherapy.

Material and methods: This was a retrospective single-institution experience, including 229 men, clinically staged T1c-T2b, Gleason 3 + 3 (prostate specific antigen (PSA) <= 15), or Gleason 3 + 4 (PSA <= 10), consecutively treated between 2004 and 2012 with HDR brachytherapy alone, using three different fractionation schedules of 92-95 Gy (EQD(2), alpha/beta = 3). Group 4F (n = 19) had a single implant of 9.5 Gy in four fractions over 2 days. Group 3F (n = 107) had three separate implants of 11 Gy over 4 weeks. Group 2F (n = 103) had two implants of 14 Gy over 2 weeks. No adjuvant hormonal therapy was allowed.

Results: For 4F, 3F, and 2F study groups, median follow-up was 10.2, 7.1, and 6.1 years, respectively, and biochemical failure rate was 10.5%, 4.7%, and 14.6%, respectively. Early and late side effects were followed with common terminology criteria version 2.0 and patient-reported questionnaires. There were a temporary acute urethral toxicity increase, 1-2 grades over baseline lower urinary tract symptoms (LUTS), which usually recovered. About 1/3 of the patients had a remaining one grade over baseline LUTS. Severe grade 3-4 toxicity were only found in 3.5% of patients. No rectal toxicity was observed. Erectile dysfunction (ED) was depending on age and erectile function before treatment. In patients without ED before the treatment, we found a complete ED in 21% of men at the last follow-up.

Conclusions: In the present study, HDR mono-brachytherapy was found to be an effective treatment, with mild long-term side effects difficult to differentiate from aging effects. There were no significant differences in PSA regression, PSA failure rate, and toxicity between the different fraction schedules.

INTRODUCTION: Treating localized high-risk prostate cancer with a combination of external beam radiation therapy (EBRT) and high-dose-rate brachytherapy (HDR-BT) is a common approach. Moderately hypofractionated EBRT and a single HDR-BT boost simplifies the treatment. We aim to present our five-year results.

METHODS: In this study, 355 patients treated with moderately hypofractionated EBRT (42 Gy in 14 fractions) and a single HDR-BT boost (14.5 Gy) at Örebro University Hospital between 2008 and 2018 were included. They were followed with regular PSA tests.

RESULTS: The median age of the cohort was 70 years (range: 51-81) and the median follow-up duration was 56 months (range: 6-150). Among them, 45% were classified as very high-risk, 38% as high-risk and 17% as intermediate-risk. Adjuvant androgen deprivation therapy (ADT) with a median duration of 24 months was given to 75% of the patient cohort. The estimated 5-year failure free survival rates were 79% (whole cohort), 66% (very high-risk), 90% (high-risk) and 85% (intermediate-risk), respectively. Initial PSA > 10 ng/mL, Gleason score 9-10 and tumor stage T3 were significantly associated with biochemical failure (BF). A PSA bounce occurred in 53 (15%) cases and was inversely associated with BF (p = 0.001) for patients receiving ADT.

CONCLUSIONS: Moderately hypofractionated EBRT and a single HDR-BT boost seems to be an effective treatment against intermediate- and high-risk localized prostate cancer. Treatment escalation strategies should be investigated for very high-risk patients where the risk of recurrence remains high.