ESTRO 38 Abstract book

S142 ESTRO 38

years, biochemical disease-free survival was 70% (95% CI 52-93%) and metastases-free survival was 93% (95% CI 85- 100%) (Figure 2).

Conclusion Focal salvage MRI-guided HDR-BT leads to high tumor control with low severe toxicity rates and short, self- limiting increases in urinary complaints. OC-0286 Focal high-dose-rate brachytherapy for localized prostate cancer: long-term clinical follow-up. M. Van Son 1 , M. Peters 1 , M.A. Moerland 1 , J.J.W. Lagendijk 1 , J.R.N. Van der Voort van Zyp 1 1 UMC Utrecht, Radiotherapy, Utrecht, The Netherlands Purpose or Objective Focal treatment of localized prostate cancer is an emerging paradigm in the search of optimal patient- tailored therapies with minimal toxicity. Though whole- gland treatments such as radiotherapy or prostatectomy reach excellent tumor control rates, they are associated with toxicity and quality of life (QoL) deterioration. Focal high-dose-rate brachytherapy (HDR-BT) may reduce toxicity and thereby preserve QoL in a selected patient group. Here we present long-term follow-up data. Material and Methods Thirty patients with localized prostate cancer were treated with focal HDR-BT between May 2013-April 2016. Local disease status was evaluated by systematic biopsies and 3T MRI, using multiparametric MRI for the last 5 patients. After the brachytherapy implant procedure, 1.5T MRI’s were made for organ contour adjustments and a final check of catheter positions. In a single dose, 19 Gy was delivered to the tumor area with a margin of 5 mm. Before treatment and during follow-up, genitourinary (GU) toxicity, gastro-intestinal (GI) toxicity and erectile dysfunction (ED) were graded according to the Common Toxicity Criteria for Adverse Events (CTCAE) 4.0. In addition, International Prostate Symptoms Score (IPSS) and International Index of Erectile Function score (IIEF-5) were obtained. QoL was measured with validated questionnaires (RAND-36, EORTC QLQ-C30 and EORTC QLQ-PR25). PSA was monitored, with biochemical recurrence defined as nadir+2 (Phoenix definition). Results At baseline, median PSA was 7 ng/ml (range 1-10), median PSA doubling time was 4.5 years (range 0.5-38) and highest Gleason grade was 4+3=7 (2 patients). All tumors were stage T2. One patient received 1x45 mg Eligard 3 months before treatment. Median follow-up was 48 months (range 19-60). Improper removal of a brachytherapy catheter caused acute hemorrhage of the prostate in one patient. No grade >2 GU (Figure 1) or GI toxicity occurred and ED was relatively stable throughout follow-up. Mean IIEF-5 score decreased from 14 at baseline to 9.5 after 6 months, remaining stable around 10 afterwards (moderate ED, p<0.01). Mean IPSS increased in the first month from 6 to 9 (moderate symptoms, p=0.02), returning to baseline- level afterwards. There were no significant differences in QoL. Biochemical recurrence occurred in 10 patients, of which 9 had local recurrence on imaging (two in-field recurrences). Five patients were re-treated with curative salvage treatments. Two patients started ADT. After 4

Conclusion In terms of toxicity, focal HDR-BT is a safe treatment. Apart from one perioperative complication (3%), no grade >2 GU or GI toxicity occurred. Patient-reported QoL did not decrease over time. However, long-term biochemical control is inferior to whole-gland treatments. This might in part be attributed to inadequate patient selection. OC-0287 Dose to the dominant intraprostatic lesion using HDR vs. LDR monotherapy: Phase II Randomized trial J. Crook 1 , D. Batchelar 2 , M. Hilts 2 , D. Anderson 2 , F. Bachand 1 , S. Tissaverasinghe 1 , B. Farnquist 3 , T. Bainbridge 4 , C. Araujo 2 1 BC Cancer Agency - Southern Interior, Radiation Oncology, Kelowna, Canada; 2 BC Cancer Agency - Southern Interior, Radiation Physics, Kelowna, Canada ; 3 Kelowna General Hospital, Radiology, Kelowna, Canada ; 4 Kelowna General Hospital, Pathology, Kelowna, Canada Purpose or Objective To present the dosimetric results of a Phase II randomized trial comparing dose escalation to the magnetic resonance imaging(MRI)-defined dominant intraprostatic lesion (DIL) using either low dose rate (LDR) or high dose rate (HDR) Patients receiving prostate brachytherapy as monotherapy were randomized to LDR or HDR brachytherapy. Prostate and DILs were contoured on pre-operative multiparametric MRI. These images were registered with transrectal ultrasound (TRUS) for treatment planning. LDR brachytherapy was preplanned using I-125 seeds. Postplan dosimetry was performed at day 30 using MR-CT (computed tomography) fusion. HDR brachytherapy used intra-operative TRUS-based planning to deliver 27 Gy/2 prostate brachytherapy Material and Methods