Biochemical outcome of prostate cancer patients treated with hypofractionated external radiation and a single high-dose-rate brachytherapy boost.

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.