Partial or whole gland brachytherapy to maintain erections

Rationale: A drawback of the standard whole gland brachytherapy for prostate cancer is that large volumes of sensitive organs and structures are irradiated to a high dose. The unavoidable dose on these organs and structures will lead to unwanted late effects. Reducing the irradiated volume for a selected group of patients with unilateral low-risk significant disease can reduce the probability of late effects. The hypothesis in this study is that by performing hemigland brachytherapy the incidence of erectile dysfunction can be reduced by 20%.



Objective: The main objective is to assess if partial prostate brachytherapy will lead to less erectile dysfunction than whole gland prostate brachytherapy.

Secondary objectives are:

- To assess differences in urinary and rectal late effects between whole gland and partial prostate brachytherapy.

- To assess differences in post-procedural quality of life measured by EORTC QLQ- C30 and QLQ-PR25 questionnaire.

- To assess the local oncological efficacy as measured by the proportion of men who are free of local prostate cancer in the two different groups. This will be examined by standardized 12 core prostate biopsies and mpMRI.



Study design: This study is designed as a randomized study between whole gland prostate brachytherapy (control arm) and hemigland prostate brachytherapy (experimental arm). Study population: The study population consists of patients with proven unilateral significant adenocarcinoma of the prostate. The tumour is unilateral localised by histopathology and mpMRI. The accepted clinical stages are T1c-T2b with (Gleason 3 + 3 with ≥30% tumor of all taken cores and PSA ≤ 20 ng/ml) or (Gleason 3+4 or Gleason 4 + 3 and PSA ≤ 15 ng/ml). Eligible patients are sexually active. Intervention (if applicable): All patients are treated with brachytherapy either on the whole gland or hemigland. The treatments are performed with a permanent implantation with I-125 sources or a temporary implantation with HDR.



Main study parameters/endpoints: The primary endpoint is deterioration of erectile function by assessment of the IIEF-5 score. A drop of at least 5 points compared to baseline value or a need to start with a phosphodiesterase 5 inhibitor (PDE5 inhibitor) (or other medical interventions to improve erections) at last follow-up is considered as an event. Nature and extent of the burden and risks associated with participation, benefit and group relatedness: The treatment burden will not be much different than what is common for the standard whole gland brachytherapy. After the regular diagnostics patients will be treated either on a same admission-day policy or a short hospitalisation. That will not be different between the two study arms. To be eligible for this study extra investigations will be performed, such as template prostate biopsies and mpMRI, which is not standard practice everywhere. In the follow-up, late effect and quality of life forms need to be filled in by the patients and standard 12 core prostate biopsies and mpMRI will be performed.

When only a part of the prostate is treated there is evidently a risk to undertreat and jeopardize the patient’s life. For this reason a non-inferiority analysis will be conducted to test the safety of partial treatment.

Hemigland prostate brachytherapy will reduce the absolute incidence of erectile dysfunction by 20% compared to whole gland prostate brachytherapy

Accrual time 3 years.

Minimal follow-up time 5 years.

Prostate brachytherapy either I125 (144 Gy) or HDR (2 x 13.5 Gy).



Control arm: Whole gland brachytherapy

Experimental arm: Hemigland brachytherapy