ESTRO 2021 Abstract Book

S1688

ESTRO 2021

improved, tolerance was acceptable and no toxicity was observed. Five patients re-irradiated are still alive at this moment. No acute effects during radiation or late toxicity greater than grade 2 have been related with CNS radiotherapy. No routinely corticoid treatment was needed or recommended starting RT treatment Conclusion Although childhood CNS tumors have significant mortality and morbidity, in our experience with modern radiotherapy techniques we have obtained good results with low toxicity. Re-irradiation is an option that can safely improve symptoms and prolong survival. Further studies are needed to assess the roll of new fractionated cranial irradiation and re-irradiation in pediatric patients. PO-1986 Early toxicity with stereotactic body radiation therapy for prostate cancer J. Saavedra Bejarano 1 , M. Rubio Jimenez 1 , P. Vicente Ruiz 1 , M. Ortiz Seidel 2 , M. Márquez García-Salazar 1 , A. Illescas Vacas 1 1 Hospital Universitary Virgen Macarena, Oncology Radiotherapy, Seville, Spain; 2 Hospital Universitary Virgen Macarena, Medical Physics, Seville, Spain Purpose or Objective Stereotactic body radiotherapy (SBRT) has proven to be a new option for localized prostate cancer. SBRT specific indications has been transformed due to SARS-2-COVID19 scenario. This communication shows our data about acute toxicity in patients treated with SBRT during the last sixteen months. Materials and Methods This retrospective and observational study was performed on prostate cancer patients admitted into our radiotherapy department for SBRT between October 2019 until January 2021. SBRT treatment at our institution has been standardized as an IGRT technique using VMAT radiation therapy due to deliver total doses of 36.25 or 40 Gy in 5 fractions. The following variables were recorded: age, past medical history, previous treatment with anticoagulant or antiplatelet drugs, Performance Status (PS), ACE-27 score, IPSS score, Gleason score, Prostate Volume, Tumor Stage, PSA levels, Risk group following NCCN, Hormonotherapy, Radiation Area, RT Doses as well as different toxicity types depending on Genitourinary (GU) or Gastrointestinal (GI) location. Toxicity review was recorded (after RT, six month and 12 months) according to Common Terminology Criteria for Adverse Events (CTCAE). For the descriptive analysis, analytical variables were represented using absolute and relative frequencies. All statistical analysis were conducted using software from SPSS (version 25.0, Chicago, IL). The hypothesis of our study is SBRT technique will reduce radiotherapy sessions with a low rate of toxicity. Results A total of 47 patients were included, with a median age of 71 years, performance status 0-1, including high risk prostate cancer (25 patients with Gleason score 6, 17 with score 7, 4 with score 8 and 1 with score 9), all of them without seminal vesicles affected. Related to NCCN risk group, 57.4 % of the patient had very low risk, low risk and favorable intermediate risk and 42.6% were unfavorable intermediate, high and very high risk. Androgen deprivation was associated in 40.4% of the cases with a median of treatment in six months (RI:6-24). Image Guided Radiotherapy was performed by matching of fiducial markers on kvCBCT images that were acquired prior to treatment, for positioning, and during treatment, for intrafraction movement control in 74.5% of the patients. The remaining 25.5% were treated by means of a gating system guided by continuous transperineal ultrasound scanning (Clarity ®system). Acute toxicity grade 1 and 2 after RT was greater at GU (51.1%/21,3%) than GI (12.8%/4.3%) location. During subsequent follow-up no patient developed acute GU or GI toxicity greater than or equal to grade 2. At 6 and 12 months evaluation GU toxicity was greater than GI, 31.7% Vs. 17.1% and 12%Vs.4%, respectively. Conclusion Evaluation of toxicity during the early phase SBRT has proven to be a well tolerated treatment for prostate cancer in our series. PO-1987 Developing an in-house adaptive radiotherapy training package for therapeutic radiographers M. Rashid 1 , S. Reinlo 2 , C. Shelley 1 , L. Conway 1 1 Royal Surrey County Hospital, Radiotherapy, Guildford, United Kingdom; 2 Royal Surey County Hospital, Radiotherapy, Guildford, United Kingdom Purpose or Objective Currently in our institution, treatment therapeutic radiographers (RTTs) are fully trained in online soft tissue matching of spefic treatment sites, however are not involved in the planning of patients’ treatments – this is performed by a dedicated planning team and the patient’s oncologist. Online adaptive radiotherapy (oART) with daily replanning requires the daily outlining of organs at risk (OAR) to create a treatment plan based on the position of the patient’s anatomy on that day, rather than on the planning CT scan taken several weeks previously. The target volumes are then generated and evaluated, before a decision on the best treatment plan (adapted or original plan) is made. At our institution this process is currently performed by a clinician, with the aim for RTTs to take on this process in the future. The purpose of this project was to establish the baseline knowledge and skill level of RTTs and determine the additional training required for them to be able to perform daily oART. Materials and Methods We designed an online survey to gather information regarding previous training and educational experience of oART, as well as areas where RTTs felt the need for additional training and how this should be given. The survey was distributed to RTTs in our department in December 2019 and the results were collated in Microsoft Excel. Results 55 surveys were circulated with 23 replies giving a response rate of 42%. The survey revealed that 74% of RTTs had not been taught about oART during their undergraduate education. For those with oART knowledge, this had predominantly come from self-directed learning. As shown in Figure 1, post qualification, 53% of RTTs had received training in contouring, 68% in assessing target volume coverage, and 47% in plan selection (these were mainly RTTs that had been involved in a previous oART clinical trial). Figure 2 shows the areas where RTTs felt they needed the most training, the majority specified plan Digital Poster: Education and training/role development