ESTRO 36 Abstract Book

S721 ESTRO 36 _______________________________________________________________________________________________

based SBRT was performed with Volumetric Modulated Arc Therapy in its RapidArc form and flattening filter free beams. The treatment schedule was 35 Gy in five fractions delivered on alternate days. The PTV included the prostate for low risk and prostate plus seminal vesicles for intermediate risk, with a 5 mm margin in all other directions. Toxicity was recorded according to CTCAE criteria v4.0. Biochemical failure was calculated according to the Phoenix definition. The Expanded Prostate Cancer Index Composite questionnaire was used to record health- related quality of life. Results From May 2012 to April 2016, 50 patients were enrolled. Twenty-five patients were classified in low risk group and 25 in intermediate risk group. Mean age was 78 years old (range 75 – 84); Gleason score was 6 in 26 and 7 in 24 patients. Median initial PSA was 6,43 (range 2,6 – 17). Median follow-up was 26 months. Acute toxicity was mild. Rectal toxicity was reported as grade 1 in 5 (10%) cases and grade 2 in 1 (2%) cases; grade 1 and grade 2 genitourinary toxicity was described in 13 (26%) and 14 (28%) patients, respectively. In the late setting, 3 (6%) patients reported rectal grade 1 toxicity. Genitourinary late effects were reported as grade 1 in 13 (26%) patients and grade 2 in 2 (4%) patient. Regarding outcome, median nadir PSA was 0.51 ng/ml (range 0.01 – 3.12). Trend of PSA is reported in Figure 1. No biochemical relapses were observed during follow-up and all patients are alive at the moment of the analysis.

(FU) were included. Late grade ≥2 gastrointestinal (GI) or genitourinary (GU) toxicity was evaluated using physicians charts and EORTC-RTOG toxicity questionnaire at 3, 6 and 12 months and yearly thereafter. The highest score of both was used to identify toxicity. Between 2010-2013, validated self-assessment questionnaires, EORTC QLQ-C30 for health-related QoL and EORTC PR-25 for PCa-specific QoL, were yearly sent to all patients. All C30 functioning domains, global health and fatigue and pain symptoms were evaluated. The evaluated PR25 domains were sexual activity and functioning, urinary and bowel symptoms, and incontinence aid use. Raw scores of each domain were linearly transformed into 0-100 scales. Higher functional scores indicate higher functioning and better QoL, while higher symptom scores indicate lower QoL. Patients with toxicity were compared to patients without late toxicity. A multi-level linear model was used to statistically assess the QoL differences between the 2 groups over 6-10 years FU. Covariates were included in the analysis to control for their influence: age, PSA, prostate volume and FU time. Clinical relevance of the differences was assessed by means of the minimally important difference (MID): toxicity group mean scores ≥0.5 standard deviation different from the non-toxicity group, were considered clinically relevantly different. Results Late grade ≥2 toxicity was reported by 79 patients (46.2%), of whom 57 (33.3%) had GU and 30 (17.5%) had GI symptoms. Of both C30 and PR25, 364 questionnaires were analysed (mean 2.1 per patient). Generic QoL (C30)domains did not show any statistically significant differences (Table 1). PR25 PCa-specific QoL for both urinary and bowel symptoms showed clinically relevant worse QoL scores for patients with grade ≥2 toxicity (p<0.001 and p=0.01, respectively). Of sexually active patients, patients with toxicity reported better sexual function (p=0.001); which was also clinically relevant. The included covariates did not show any associations with QoL score differences.

Conclusion Gantry-based SBRT with VMAT and FFFs can be considered an effective, non-invasive and safe approach for elderly patients affected by prostate cancer at low and intermediate risk. Randomized trials comparing SBRT with other approaches in this setting are necessary. EP-1344 Long-term quality of life after high-dose-rate brachytherapy boost for prostate cancer W. Busser 1 , I. Korfage 2 , S. Aluwini 1 1 Erasmus MC Cancer Institute, Radiation Oncology, Rotterdam, The Netherlands 2 Erasmus Medical Center, Public Health, Rotterdam, The Netherlands Purpose or Objective Quality of life (QoL) of patients treated for prostate cancer (PCa) is relevant because of the long survival of these patients. We aimed to report late toxicity incidences and generic and PCa-specific health-related QoL and to investigate associations between toxicity and QoL in patients treated with high-dose-rate brachytherapy (HDR-BT) boost combined with external beam 264 low- and intermediate risk PCa patients were treated between 2000-2007 with single implant HDR-BT boost (3x6 Gy) combined with EBRT (25x1.8 Gy). Of these, 171 patients with QoL data available with 6-10 years follow-up radiotherapy (EBRT). Material and Methods

Conclusion For patients treated with EBRT and HDR-BT boost, late grade ≥2 toxicity was not associated with decreased QoL for generic QoL domains, but associations between toxicity and decreased PCa-specific QoL scores were observed. The higher sexual functioning scores in the toxicity group are hard to explain and worth more investigation. EP-1345 Dosimetric effect of seed-based prostate localisation on Pelvic Lymph Nodes in High-Risk Prostate Ca R. Valentine 1 , E. Miguel Chumacero 2 1 NHS greater glasgow and clyde, Department of Radiotherapy Physics, glasgow, United Kingdom 2 NHS greater glasgow and clyde- University of Glasgow, Department of Radiotherapy Physics, Glasgow, United Kingdom