ESTRO 2020 Abstract Book

S1067 ESTRO 2020

conducted. All patients were treated under free breathing with real time motion tracking image-guided RT. The OS was calculated using Kaplan-Meier method and the post RT toxicity data was scored following the CTCAE v4.0 protocol. Assuming a/ß=10 for tumour control, the biological equivalent doses (BED) of prescribed treatment were calculated. For subgroup analysis of prognostic factors, medians were used to categorise patients into 2 groups: £median and > median. A Mantel-Cox log-rank analysis was used to assess OS between these groups. Results In between July 2011 to July 2018, 20 patients with inoperable pancreatic cancer who received SABR (either 3 or 5 fractions) at our institution were included in this study. The median follow-up was 9.6 months (range 1.0- 34.2). 60% of the patients received chemotherapy prior SABR and none of them were treated with concurrent chemotherapy during SABR. The median OS was 9.2 months (95%CI 5.9-12.5) and the OS at 12months was 35%. Acute and late side effects from stereotactic treatment include fatigue, nausea and bowel disturbance. 50% of patients reported grade 1 and grade 2 fatigue within 12 months post completion of RT. No greater than grade 3 post RT toxicity has been reported in this cohort. No statistically significant differences in OS were found when comparing the median groups of patients’ ages, the number of fractions, chemotherapy prior SABR status, BED, gross tumour volume (GTV) and planning target volume (PTV) sizes (p>0.05 of all factors). Conclusion The use of SABR in our cohort of patients with inoperable pancreatic cancer has shown promising OS rates irrespective of patients’ ages, the number of fractions, prior chemotherapy status, BED, GTV and PTV sizes, with an excellent post-RT toxicity profile. PO-1913 A Study on the Dose Difference of Target in Treatment of Prostate with Real-Time MRI Imaging Y. Lee 1 1 Seoul National University Hospital, Radiation Oncology, Seoul, Korea Republic of Purpose or Objective The prostate in the pelvis is severely affected by the surrounding internal organs, the rectum, bladder, etc., and is particularly affected by intestinal gas. It is necessary to be able to take into account the movement according to the change of internal organs or the amount of gas. For this purpose, IGRT using OBI or CBCT treats the prostate, The prostate is difficult to treat properly because of the large change of motion due to intestinal gas. Therefore, it is necessary to treat with MRI guided technique which can see the soft tissues well. This study is to evaluate the appropriateness of treatment for each organ according to planned doses based on real - time imaging with MRI in the treatment of prostate. We evaluate the proper treatment of organs in accordance with the treatment plan according to the treatment plan based on real-time MRI imaging using the Viewray MRIdian System (Viewray, Viewray Inc, OH.USA). Material and Methods This study was a retrospective study that analyzed a total of 630 data from 18 patients who were treated from March to September, 2018. The data were analyzed for age, age and treatment time. In addition, to determine the effect on bowel

movements, the subjects who are enema and those who do not enema are divided into two groups. The treatment group was divided into 36.25 Gy, 5fx, 13 people and 70Gy, 28fx, 5 people. The 36.25 Gy group was injected with a prescription drug each time, and the contents of the rectum before treatment were evacuated and the 70 Gy group was excreted only. Results The 36.25 Gy group mean age was 74.9 years, treatment time was 555.1 seconds, dose was 100.7%, standard deviation was 2.7%. The 70 Gy group average was 72.4 years old, the treatment time was 229.3 seconds, the dose was 100.3%, and the standard deviation was 1.4%. Errors were observed in Bowel 31%, Bladder 13.1% Rectum 15.9% in one treatment. p value was Dmean, Dmax, age, treatment time was less than 0.01, and the difference between the two groups was reliable. The mean dose between the two groups was 0.9 ∼ 0.3%. The most significant difference was 0.9% in Rectum. CTV and Bowel were the sites with the minimum dose difference. Rectum was 0.7% where the standard deviation was high. Especially, the standard deviations of Mean, Max, and Min dose were 4.7%, 4.7%, and 13.6%, respectively, even though Adaptive RT was performed by MR-IGRT for one IGRT enables highly accurate treatment at the treatment site. However, this treatment only considers anatomical position based on bone density. so it can cause side effects due to soft tissue movement. It gives large doses to the rectum and small intestine or insufficient dose to the target area.Therefore Real-time MR images should be obtained to check for errors to reduce side effects. In addition, this study showed that treatment with enema every time can help to reduce dose to rectum and small intestine. Therefore, if possible, it may be appropriate to minimize bowel movements through the enema to reduce side effects during treatment. PO-1914 Patient compliance during Deep Inspiration Breath Hold for left breast cancer radiotherapy M. Marson 1 , A. Ferretti 1 , C. Angela 1 , A. Vendrame 2 , C. Cristina 2 , P. Chiovatti 2 , L. Vinante 1 1 Centro di Riferimento Oncologico di Aviano- IRCCS- Aviano IT, Radiation Oncology, aviano, Italy ; 2 Centro di Riferimento Oncologico di Aviano- IRCCS- Aviano IT, Medical Physics, Aviano, Italy Purpose or Objective Voluntary deep inspiration breath hold (DIBH) technique is used to heart sparing during left breast cancer radiotherapy. Patients compliance is a determinant aspect of DIBH. The aim of this study is to investigate the role of patient training and audio coaching system during DIBH treatment to increase patient compliance. Material and Methods From February 2019 to September 2019, 39 patients received hypofractionated (15 fractions) whole breast radiation with IMRT technique in DIBH. Patient age ranged between 37 and 77 years old. All patients had an high cardiovascular risk due to personal anamnesis or prior cardiotoxic chemotherapy. Patients coaching started during the physician visit when received an informative explanation of the procedure and are encouraged to try breath hold at home. Computer tomography simulation was performed using a real-time position management (RPM) system to verify the reproducibility of DIBH and select the treatment’s DIBH thresolds. Patients set-up was daily controlled by orthogonal kv x-rays. Images were online reviewed and position were always corrected before treatment. During the radiation treatment patients were guided by the operator through an audio system to the established thresholds. The treatment’s period of every treatment. Conclusion