Marieke van Son

99 MRI-GUIDED ULTRAFOCAL SALVAGE HDR-BRACHYTHERAPY a course of radiotherapy. 30 Adversely, an increased number of fractions and associated overall treatment time could affect the radiation tolerance of normal tissue. In a small study by Murgic et al., 15 patients were treated with focal salvage HDR-BT using a prescription dose of 27 Gy divided over two implants with a one week inter- val. 14 Treatment was aimed at the quadrant of the prostate containing an MRI-visible recurrent lesion. Staging included 3T mp-MRI, CT and bone scan. Their patient group was comparable to our cohort, except they had no primary T3 tumors versus 26% in our cohort. After three years, BDFS was 61%. One patient (7%) had severe (grade 3) late GU toxicity, 14 patients (93%) had acute grade 2 GU toxicity and no severe GI toxicity occurred. The relative biochemical control benefit of this regimen therefore seems to come with more toxicity. For the future, our challenges are to improve patient selection and treatment tech- nique. Our cohort represents a wide variety of patient and tumor characteristics, all with varying risks of treatment failure. Overall oncologic control statistics are therefore not generalizable. However, there is a lack of knowledge on how to stratify risk groups in the radiorecurrent setting. A prediction model for failure is warranted to indicate which patients benefit most from focal salvage treatment. 5