ESTRO 2023 - Abstract Book

S516

Sunday 14 May 2023

ESTRO 2023

Conclusion Among men with intermediate-risk prostate cancer, FFBF was statistically unfavorable for BT-M, although both BT-M and BT-B achieve excellent long-term biochemical and survival rates. On the other hand, long-follow up showed that late grade 3 GU toxicity was statistically unfavorable for the BT-B group. Late grade 3 or higher GI toxicity was limited in both groups, but there were fewer late effects in the BT-M group. OC-0626 HDR-BT and SBRT in prostate cancer: results from a prospective phase II trial NCT04523896 D. Buchser Garcia 1 , A. Bilbao 1 , M. Marban 1 , J. Cacicedo 1 , F. Perez 2 , I. Valverde 2 , J.M. Espinosa 2 , B. Santos 3 , F. Casquero 1 , A. Gomez-Iturriaga 1 1 Hospital Universitario Cruces, Radiation Oncology, Barakaldo, Spain; 2 Hospital Universitario Cruces, Radiation Physics, Barakaldo, Spain; 3 Biocruces Health Research Institute, Epidemiology and statistics, Barakaldo, Spain Purpose or Objective To report late toxicity, disease control and impact on QoL in patients treated with a combination of HDR prostate brachytherapy and prostate SBRT for intermediate and high-risk prostate cancer in a phase II prospective trial. Materials and Methods In this prospective phase II trial, a total of 72 patients with intermediate (IR) and high risk (HR) prostate cancer were recruited to receive a combination of real time HDR-BT 15 Gy followed by SBRT to the prostate: 5 fractions of 5 Gy each delivered in consecutive days with or without short or long-term androgen deprivation therapy (ADT). Image-guided RT through intrafraction fiducial marker monitoring was used for SBRT. All patients underwent a diagnostic mpMRI of the prostate. Genito-urinary (GU) and gastro-intestinal (GI) toxicity was assessed according to CTCAE v5. Patient QoL was evaluated through ICHOM (international consortium for health outcomes measurement) methodology with EPIC and EORTC QLQ-PR25 questionnaires. A decreased of > 0.5 standard deviation of baseline values was considered clinically relevant. The proportion of patients showing biochemical failure (PSA NADIR + 2 ng/mL), metastatic failure or death from prostate cancer was studied. Results Sixty-three patients (NCCN 56,9% IR and 43,1% HR) completed treatment and reached at least 12 months of follow-up (FU) at the time of the current analysis. Median FU was 29 months (IQ range 20-36). Median age was 75 years, median PSA before treatment was 7.1 ng/mL (5.6-11.2) and median volume of the prostate was 33 cc (27-43.5). Short-term ADT was administered to 22,2% of patients whereas 37,5% received long-term ADT, the rest of the patients did not receive hormonal therapy. No severe (i.e. G3-4) acute or late events were recorded. The cumulative incidence of acute G2 GU and GI events were 14.7% and 1.6% respectively. The most common acute GU symptom was dysuria whereas the most common acute GI event was proctitis. The cumulative incidence of late G2 GU events was 12.7% whereas no G2 late GI event was observed. The most common late GU symptom was nocturia. No significant decline in patient QoL was observed in any of the domains studied (urinary, bowel, sexual and hormonal). Only 1.6% of patients (1 patient) had a biochemical failure. No metastatic failures or deaths attributable to prostate cancer were recorded. Median PSA nadir was 0.04 ng/mL (IQ range 0.02-0.28). Conclusion This prospective phase II trial confirms that the combination of 15Gy HDR prostate brachytherapy and prostate SBRT (25 Gy in 5 daily fractions) is a well-tolerated scheme, and no severe adverse events were recorded. Moreover, patient reported outcomes confirm these results, we could not find a significant decline in any domain from baseline values. This approach shows promising disease control data that warrants further investigation. OC-0627 Prospective study of MRI guided HDR-BT and EBRT: 10years experience of a mono-institutional cohort A. Gomez Iturriaga 1 , I. Valverde-Pascual 2 , F. Perez Azorin 3 , B. Santos-Zorrozua 4 , J.A. Guerrero 5 , F. Couñago 6 , J. Cacicedo 7 , M. Marban 7 , I. San Miguel 8 , I. Raton 7 , C. Mascarell 7 , D. Büchser 7 1 Hospital Universitario Cruces, Biocruces Bizkaia Health Research Institute, Radiation Oncology, Barakaldo, Spain; 2 Hospital Universitario Cruces, Biocruces Bizkaia Health Research Institute, Radiation Physics, Barakaldo , Spain; 3 Hospital Universitario Cruces, Biocruces Bizkaia Health Research Institute, Radiation Physics, Barakaldo, Spain; 4 Biocruces Bizkaia Health Research Institute, Cruces University Hospital,, Scientific Coordination Unit, Barakaldo, Spain; 5 UPV/EHU, Surgery,