ESTRO 2020 Abstract Book

S627 ESTRO 2020

from International Journal of Radiation Oncology, Biology, Physics. Remarkably, there are clear recommendations for the treatment of PCB. The most focus of PCB is to increase long-term outcome and quality of life. PO-1191 SIB-VMAT for DIL in prostate cancer: the preliminary result in acute toxicity and quality of life W. Sittiwong 1 , P. Dankulchai 1 1 Division of Radiation Oncology- Department of Radiology- Faculty of Medicine Siriraj hospital- Mahidol University, Radiology, Bangkok, Thailand Purpose or Objective The most common site of recurrence of prostate cancer after definite radiation therapy is the dominant intraprostatic lesion (DIL).This study aims to investigate the feasibility and the safety of definite volumetric modulated arc therapy (VMAT) with simultaneous integrated boost (SIB) to DIL in patients with unfavorable intermediate to high risk prostate cancer. Material and Methods This is a prospective, uncontrolled clinical trial of SIB to DIL in patients with unfavorable intermediate to high risk prostate cancer. Patients were delivered definitive VMAT with the dose of 87.75 Gy (92 Gy α/β=3 EQD2) to DILs and the dose of 78 Gy to whole prostate gland in 39 fractions. All patients were implanted with three gold seeds and daily position verification based on implanted fiducial markers was performed by using in-room X-Ray based monitoring system (ExacTrac®). Treatment-related side effects in terms of acute GU and rectal toxicity were collected using the Common Toxicity Criteria for adverse event (CTCAE) version 5.0 during each follow-up visit. International Prostate Symptom Scores (IPSS) and quality of life (QOL) due to urinary symptoms in Thai language version were also collected at baseline before treatment and then each follow-up visit. Toxicity and patient reported outcomes were reported on maximum score at 4 weeks after completion of treatment. Results During December 2018 to September 2019, 17 patients who completed 39-fraction VMAT were included for the preliminary report on acute toxicity analysis. All patients were prescribed androgen deprivation therapy. The rates of grade 2 acute genitourinary (GU) toxicity were 35.3%. There was no acute ≥ grade 3 GU toxicity. There was one patient (5.8%) developed grade 3 acute rectal toxicity; whereas, no patient developed grade 2 acute rectal toxicity. Median IPSS at baseline before treatment was 6 (range, 1 to 14) and the mean changes in IPSS during the treatment was +5.94 points (range, 1 to 12). At 4 weeks after radiotherapy, the means changed in IPSS was +0.41 points (range, -8 to +8). For the IPSS-QOL scores, all patients had baseline QOL scores in pleasant range (score 0 or delighted to score 2 or mostly satisfied). During the treatment, 7 patients (50%) rated QOL scores in the unpleasant range (4 or mostly dissatisfied to 5 or unhappy). However, at 4 weeks after radiotherapy, the QOL scores decreased to be the same as the baseline scores in all patients.

Conclusion This preliminary report demonstrates that SIB to DIL in prostate cancer patients resulted in similar rates of acute toxicity compared with the results in previous studies of 78-Gy definite radiation without DIL boost. The IPSS scores and IPSS-QOL scores significant increased during the treatment; however, at 4 weeks after the treatment, the scores declined to be equivalent to the baseline. Nevertheless, to ensure that this focal dose escalation technique was safe and feasible, further reports with long- term follow up will be conducted to evaluate the late- toxicity profiles. PO-1192 Elective Pelvic Nodes Irradiation in Patients with Prostate Cancer (PRO-EPI Study) M. Buglione 1 , A. Bruni 2 , L. Bardoscia 1 , S. Borghesi 3 , E. Mazzeo 2 , C. Cozzaglio 4 , G. Mortellaro 5 , L. Triggiani 1 , R. Santini 6 , R. Lisi 7 , M. Valeriani 8 , L. Amara 9 , E. Cagna 10 , S. Fondelli 11 , A.M. Alitto 12 , C. Franzese 13 , P. Muto 14 , A.