Feasibility of MRI-guided focal salvage high-dose-rate brachytherapy for locally recurrent prostate cancer

Prostate cancer recurrences after primary treatment are common, despite improvements in primary curative treatment modalities. Various salvage treatment modalities, such as radical prostatectomy, low-dose-rate brachytherapy, external beam radiotherapy, HIFU (high intensity focused ultrasound) and cryosurgery have been investigated. However, because of high failure and high toxicity rates, these treatment modalities remain unpopular. High failure rates can be reduced by excluding patients with a high risk for early distant metastases. In these patients, local salvage treatment will not be of any benefit. High toxicity rates can be explained by the fact that salvage therapy is often aimed at the entire prostate. With radiation treatment, this causes an accumulation of irradiation dose to normal tissues. To reduce the burden of radiation treatment, focal therapy is warranted. This can be achieved with MRI-guided focal salvage HDR-BT (high-dose-rate brachytherapy). In the past, focal salvage treatment was not feasible, because determination of the exact tumour location was not precise. Currently, our radiotherapy centre has an MRI HDR-BT facility, allowing MRI-guided catheter placement and treatment. Under MRI-guidance, catheter placement can be done far more accurately, which makes focal treatment possible. Due to the steep dose fall-off in brachytherapy, low radiation doses are expected in the surrounding healthy tissues. Therefore, patients will experience less toxicity of the organs at risk. In earlier studies, results regarding toxicity are promising. Therefore, we expect that MRI-guided salvage treatment by using HDR-BT will be of benefit in patients with recurrent prostate cancer.

The purpose of this study is to evaluate toxicity and feasibility of MRI-guided focal salvage high-dose-rate brachytherapy (HDR-BT) in patients with locally recurrent prostate cancer. In comparison with whole-gland salvage techniques, focal treatment is expected to reduce toxicity, while maintaining cancer control.

The treatment includes one high-dose-rate brachytherapy procedure, administering 19 Gy in a single session.
Questionnaires will be used to assess toxicity and quality of life (before treatment, one month after treatment, every 3 months the first year, every 6 months the second year, thereafter once a year for up to 10 years). For assessment of biochemical recurrence, PSA monitoring will be performed during each visit.

Follow-up time points:
4 weeks, 3 months, 6 months, 9 months, 12 months, 18 months, 24 months, 36 months, 48 months, 60 months, 72 months, 84 months, 96 months, 108 months, 120 months.

Single fraction HDR treatment to a dose of 19 Gray