ESTRO 2020 Abstract book

S405 ESTRO 2020

Cilla 2 1 Fondazione Giovanni Paolo II - Università Cattolica S. Cuore, UO di Radioterapia, Campobasso, Italy ; 2 Fondazione Giovanni Paolo II - Università Cattolica S. Cuore, UO di Fisica Sanitaria, Campobasso, Italy ; 3 Dipartimento di Medicina Specialistica Diagnostica e Sperimentale- DIMES- Azienda Ospedaliera-Universitaria S.Orsola-Malpighi, UO di Radioterapia, Bologna, Italy ; 4 PO ‘Veneziale’, UO di Oncologia Medica, Isernia, Italy ; 5 Ospedale Clinicizzato ‘SS. Annunziata’, UO di Urologia, Chieti, Italy ; 6 Fondazione Giovanni Paolo II - Università Cattolica S. Cuore, UO di Radiologia, Campobasso, Italy ; 7 Fondazione Giovanni Paolo II - Università Cattolica S. Cuore, UO di Oncologia Medica, Campobasso, Italy ; 8 Fondazione Policlinico Universitario A. Gemelli- IRCCS, Dipartimento di Scienze Radiologiche- Radioterapiche ed Ematologiche, Roma, Italy Purpose or Objective To determine the efficacy and safety of stereobody radiotherapy (SBRT) in the treatment of isolated lymph nodal recurrences in prostate cancer (PC) patients. Material and Methods Data from PC patients with nodal recurrences undergone 5 fractions (SBRT-DESTROY-1 phase I clinical trial) or single fraction radiosurgery (SRS-DESTROY-2 phase I clinical trial) as exclusive treatment, retreatment or boost after external beam radiotherapy, were collected and analyzed. From November 2003 to January 2018 patients were enrolled in different arms based on tumor site and previous treatment as per SBRT and SRS trials design. Doses ranged from 20 Gy to 50 Gy (maximum planned dose) at 4-10 Gy per fraction in DESTROY-1, while patients enrolled in DESTROY-2 trial received a single fraction dose ranging from 12 Gy to 24 Gy. Best radiologic response to treatment was evaluated by computed tomography (CT) scan, Magnetic Resonance (MR) or positron tomography (PET) scan, and classified according to the RECIST (version 1.1) or PERCIST criteria. Objective response rate included complete response and partial response. Actuarial local control (LC) was defined as the time interval between the date of SBRT and the date of inside SBRT field relapse/progression of disease or the last follow-up visit. Toxicity was evaluated by CTC-AE scale. Results Thirty-seven patients carrying a total of 60 lymph nodal lesions were selected for the enrolment. The median age was 67 years (range: 62-86), and the majority of patients (93%) presented Eastern Cooperative Oncology Group (ECOG) performance status 0-1. The most frequent anatomical districts were the pelvis (N=35, 58.3%) followed by abdomen (N=17, 28.3%), and thorax (N=8, 13.4%). Overall, dose prescription to the Planning Target Volume ranged from 16 Gy/single fraction to 50 Gy/5 fractions. The vast majority of lesions (85%) were treated with a volumetric arc radiotherapy technique. With a median follow-up of 21 months (4-89) no severe (> grade 3) acute or late toxicities were recorded, with only one patient reporting G2 toxicity (nausea). The overall objective response rate was 83.3% (CI 95%: 68.9-92.2) with a complete response rate of 80%. The 2-and 4-years actuarial LC was 88% and 69%, respectively. Conclusion This study confirms the activity and safety of SBRT in the treatment of isolated lymph nodal recurrences in PC patients. Optimal SBRT schedules should be defined taking into account the need to guarantee the best personalized radiation dose.

52% patients received anti-emetic treatment. 22% patients had a nicotinamide dose adjustment, 20% patients had a break from nicotinamide and 6% patients discontinued nicotinamide. 96% patients received carbogen with every RT fraction. One patient had an interruption of treatment and received carbogen for 33 of 37 fractions. One patient discontinued carbogen treatment after 7 fractions. No one developed G3 or worse lower GI or GU toxicities; prevalence of G1/G2 toxicities are shown in table 1. The 5 year OS and PSA-PFS rates were 92% and 87% respectively. Six patients experienced biochemical progression. Five patients have died but none had biochemical relapse prior to their death. The functional MRI analysis showed a mean decrease of 5.8% in tumour R2* after the application of carbogen, measured in 72 pairs of pre and post carbogen measurements, indicating that the carbogen exposure resulted in an immediate reduction in tumour hypoxia.

Conclusion The prevalence of acute lower GI and GU toxicities among our cohort, together with their 5 year PSA PFS and OS rates, are comparable, or superior to, those reported for patients with high risk prostate cancer receiving RT in other contemporary trials. The concurrent administration of CON with RT is safe and effective. It should be further explored in a phase III setting. PD-0667 Early analysis from two phase I trials on SBRT of isolated nodal recurrences in prostate patients F. Deodato 1 , A. Re 1 , A. Ianiro 2 , M. Ferro 1 , G. Macchia 1 , V. Picardi 1 , M. Boccardi 1 , M. Buwenge 3 , P. Assalone 4 , F. Berardinelli 5 , G. Maselli 6 , S. Cammelli 3 , M. Ferro 1 , C. Romano 2 , S. Mignogna 7 , V. Valentini 8 , A.G. Morganti 3 , S.