ESTRO 38 Abstract book

S875 ESTRO 38

experience with the onboard workflow as provided in the system including daily contour adaptation and online treatment planning based on the daily anatomy as visualized on online MRI. Material and Methods Starting August 2018, we have been treating on average 2 patients per month for pelvic and low abdominal lymph node oligometastases. Seven-beam step-and-shoot IMRT (FFF 7 MV) was used to deliver 35 Gy in 5 fractions, with a maximum of 3 fractions per week. The pre-treatment workup and actual online workflow for these treatments is illustrated in Figure 1 and consists of the following steps: 1) Pre-treatment preparation consists of CT and MR imaging, contouring based on CT and MRI, treatment planning, patient QA including film measurement and independent 3D dose calculation for the pre-treatment plan; 2) Treatment session consists of online MRI, deformable registration from pre-treatment CT to the online MRI scan, manual adaptation of GTV and organs at risk (OAR) from deformed contours if needed, full online re-planning (‘adapt to shape’ workflow with most extensive re- planning option), position verification MRI, independent 3D dose calculation, radiation delivery with intra-fraction MRI and post-fraction MRI; 3) Post treatment steps are patient QA and dose reconstruction on the intra- and post-fraction MRIs. All patients are asked to participate in a prospective observational study that investigates treatment issues and clinical outcome data, including acute toxicity and patient-reported quality of life.

in the lungs; 16.3% in the liver; 5% in lymph nodes and 2% in adrenal glands. Median diameter of the lesions was 8 mm for bone lesions, 14 mm for lung, 24 mm for liver, 12 mm for adrenal and 13 mm for lymph nodes metastases. Median follow-up was 12.1 months (ranged 2 – 35 months). Local control at 1-year (inclusive of complete, partial and stable response) was achieved in 86.5% of the treated lesions. Treatment-related grade 2-3 toxicity was observed in 4.2% of patients; grade 1 toxicity in 10.8% and no toxicity was observed in 85% of the cases. Conclusion SBRT is a safe and effective therapeutic option for the treatment of oligometastatic patients no suitable for surgery or unresectable metastases, with high local control rates, good tolerance and low treatment-related toxicity. EP-1623 KORTUC for lytic bone metastasis S. Obata 1 , O. Yukihiro 1 , T. Tatsuya 1 , M. Shigeki 1 , O. Yohiaki 1 , K. Tsunehiko 1 , K. Shinya 1 , I. Yohta 1 , K. Akira 1 , I. Kayo 1 , W. Kumiko 1 , O. Hitomi 1 1 Nagasaki Prefecture Shimabara Hospital, Department of Radiology and Radiotherapy, Shimabara, Japan Purpose or Objective To improve the effects of radiation for lytic bone metastasis, we directly injected a new radio-sensitizer into the lesion (KORTUC) under image guidance after obtaining approval from our ethics committee and informed consent. We herein report the retrospective clinical data from 25 consenting patients since 2010. Material and Methods We selected 20 eligible patients our hospital followed up. Patient age was 42-83 years, the ratio of men to women was 12: 8. As for the primary legion, lung was 12 cases, 3 rectums, 2 esophaguses, and others. Uncontrolled primary lesion was 16 cases. 16 cases accompanied other metastasis. Affected bone was 9 pelvic bones, extremities bone 5, thorax 2, and others. Performance status 3-4 was 7 cases, uncontrollable pain was recognized in 18 cases. We performed KORTUC in all cases. In half of the patients, chemotherapy, molecular targeted drug or immunotherapy was administered. Results Radiation dose was 8-54 Gy and the number of times of radio-sensitizer injection was 1-12 times. The palliative rate was 94%. 95% of the targets did not enlarge in size and half of the cases presented bone re-formation. The treatment took effect after 1-17 days and it continued for 7-630 days. The survival time was 30-1680 days. There was no severe adverse event. Neither univariate nor multivariate analysis of the local control recognized significant difference. Conclusion KORTUC for lytic bone metastasis was thought safe and effective. And a further accumulation of many cases is needed for recognition of a clinical option. EP-1624 First clinical experiences with SBRT on the 1.5 T MR-linac for pelvic lymph node oligometastases A.M. Werensteijn-Honingh 1 , P.S. Kroon 1 , D. Winkel 1 , E.M. Aalbers 1 , B. Van Asselen 1 , G.H. Bol 1 , K.J. Brown 2 , W.S.C. Eppinga 1 , M. Glitzner 1 , E.N. De Groot-van Breugel 1 , S.L. Hackett 1 , M. Intven 1 , J.G.M. Kok 1 , A.N. Kotte 1 , J.J.W. Lagendijk 1 , M.E.P. Philippens 1 , R.H.N. Tijssen 1 , J.W.H. Wolthaus 1 , S.J. Woodings 1 , B.W. Raaymakers 1 , I.M. Jürgenliemk-Schulz 1 1 University Medical Center Utrecht, Department of Radiotherapy, Utrecht, The Netherlands ; 2 Elekta AB, Scientific Research, Stockholm, Sweden Purpose or Objective The 1.5 Tesla (T) MR-linac (Unity, Elekta AB, Stockholm, Sweden) has been available for clinical use at our institute since August 2018. Our aim is to present the first clinical

Results As of October 2018, three patients have completed their full treatment course with Unity and two are currently being treated. The average daily online session duration was 41 minutes (range 33-49) including an average 34 minutes on-couch time (range 27-39). Time to completion for individual workflow items is shown in Figure 2. Target lymph nodes and surrounding tissues and organs were well visible at each treatment session allowing for contour adaptation of GTV and OAR and full online re- planning to the daily anatomy. All online treatment plans satisfied the predefined target and OAR constraints. The online independent dose calculations resulted in an average Gamma pass rate (3%/3 mm) of 97.5% (range 90.4- 99.2%). For all treatment fractions, the entire GTV received 100% of the prescribed dose (35 Gy) based on reconstruction on all online MRI scans (position verification, intra- and post-fraction). Clinical outcome data including acute toxicity and patient-reported quality of life are being collected.