S157
Brachytherapy - Urology
ESTRO 2026
Purpose/Objective: We previously reported on a prospective study that investigated the efficacy and toxicities of MR-assisted whole-gland salvage HDR prostate brachytherapy with intra-prostatic boost in patients with local recurrent prostate cancer. We present our findings updated with 6-years median follow-up. Material/Methods: Eligible patients included: multiparametric 3T MRI (mpMRI) visible biopsy confirmed local recurrence >30 months after XRT, negative metastatic workup, and IPSS <15. Ultrasound-based HDR brachytherapy was performed with intraoperative contour-based deformable registration between the mpMRI and ultrasound images (93%) or with cognitive fusion (7%). The prescription dose was 21Gy to the entire prostate and 27Gy to the MR-defined intraprostatic target volume (TV) divided over two implants separated by 1- 2 weeks with dose constraints to the urethra and rectum. Adjuvant androgen deprivation therapy (ADT) was not used. Post-treatment response was evaluated using mpMRI 1-2 years after salvage. Follow-up PSA, IPSS and CTCAE v4.0 toxicities were collected. Results: 30 patients (median age 74 years) were enrolled. Median follow-up from salvage HDR was 72.0 months (10.7-121.5). At initial presentation, there were 3, 18 and 9 low-, intermediate- and high-risk disease. The initial XRT dose was 70-78Gy with conventional fractionation in 28 patients and alternate fractionation in 2 patients (35Gy/5F, 50Gy/15F). The Gleason score of the local recurrence was 6, 7 and 8-10 in 2, 19 and 9 patients, respectively. The pre-HDR median PSA was 3.67ng/mL (0.56–11.01). The median prostate volume was 33.8 mL (15.9-86.0) and TV was 4.7mL (1.5-15.5). The median dosimetric endpoints were: prostate V10.5Gy 96.5% (94.1-98.7) and D90 11.4Gy (10.9-12.0); TV V13.5Gy 94.2% (63.3-100) and D90 18.1Gy (15.0- 22.2); urethral D10% 12.0Gy (11.5-12.6) and Dmax 12.6Gy (12.2-13.5); rectal V8.4Gy 0mL (0-0.8). Four patients (13%) required temporary urinary catheterization. The mean IPSS was stable over time (p=0.41). There were no acute or late GU/GI grade 3-5 toxicities except one patient (3.3%) with late hematuria. The PSA progression-free survival and freedom from ADT rates were 73.0% and 93.0% at 3 years, and 24.8% and 69.6% at 5 years, respectively. Of the 26 patients who had a post-HDR MRI (median 415 days), 9 (35%) had persistent disease in the TV. Of the 23 (77%) patients who had PSA relapse, 18 (78%) patients had disease in the TV confirmed by MRI, PSMA-PET, or targeted biopsy. Conclusion: Whole gland salvage HDR brachytherapy with intra- prostatic boost is well tolerated, and delays need for ADT. The predominant site of relapse after salvage treatment was in the area of initial disease.
Gleason score 6–10 received HDR brachytherapy of 27 Gy in two fractions. The primary safety endpoint was the incidence of Grade ≥ 2 gastrointestinal (GI) or genitourinary (GU) adverse events (AEs) related to radiotherapy. The primary efficacy endpoint was PSA recurrence-free survival. Eligible patients were 20–79 years old, had an ECOG performance status of 0–1, and provided written informed consent. Results: Ninety-nine patients were treated; one patient discontinued treatment. The median age was 68 years (range: 44–79), and the median PSA was 8.0 ng/mL (range: 3.64–41.8). Risk classification included 1 low-, 62 intermediate-, 26 high-, and 10 very high-risk patients. Hormone therapy was administered to 71 patients. After a median follow-up of 54 months, PSA failure occurred in three patients, and clinical relapse occurred in the three patients (one pelvic lymph node recurrence, one bone metastasis, and one local recurrence). One patient died of prostate cancer and one from another disease. Five-year PSA recurrence- free, clinical recurrence-free, and overall survival rates were 96.5%, 95.5%, and 97.5%, respectively. The cumulative incidence of late Grade ≥ 2 GI and GU AEs was 0% and 16.2%, respectively, and no Grade 3 AEs were observed. In patients with high- and very high- risk disease, five-year PSA recurrence-free, clinical recurrence-free, and overall survival rates were 97.2%, 97.2%, and 96.2%, respectively. Conclusion: HDR brachytherapy demonstrated favorable safety and promising recurrence-free outcomes in patients with localized or locally advanced prostate cancer, including high- and very high-risk disease. Long-term follow-up is ongoing. Keywords: prostate, HDR, clinical trial An updated analysis of MR-assisted whole-gland salvage HDR prostate brachytherapy with intra- prostatic boost: a prospective study Hans Chung 1,2 , Hsin-Pei Hu 1,2 , Andrew Loblaw 1,2 , Chia- Lin Tseng 1,2 , Jure Murgic 3 , Ananth Ravi 2 , Melanie Davidson 1 , Matt Wronski 1,2 , Moti Paudel 1,2 , Masoom Haider 4,5 , Deabreu Andrea 1 , Gerard Morton 1,2 1 Radiation Oncology, Sunnybrook Odette Cancer Centre, Toronto, Canada. 2 Radiation Oncology, University of Toronto, Toronto, Canada. 3 Department of Oncology and Nuclear Medicine, Sestre Milosrdnice University Hospital Center, Zagreb, Croatia. 4 Medical Imaging, Mount Sinai Hospital, Toronto, Canada. 5 Medical Imaging, University of Toronto, Toronto, Canada Mini-Oral 958
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