ESTRO 37 Abstract book

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ESTRO 37

of this study, we recommend that a well controlled study to find out optimal candidate of SBRT boost radiotherapy for locally advanced pancreatic cancer. EP-1439 MRI-based clinical target volume delineation in gastric cancer: first results of a feasibility study V.W.J. Van Pelt 1 , E.P.M. Jansen 1 , A. Bartels- Rutten 2 , J.M. Van Dieren 3 , J.W. Van Sandick 4 , C. Grootscholten 3 , U.A. Van der Heide 1 , M. Nowee 1 , M. Verheij 1 1 The Netherlands Cancer Institute, Radiation Oncology, Amsterdam, The Netherlands 2 The Netherlands Cancer Institute, Radiology, Amsterdam, The Netherlands 3 The Netherlands Cancer Institute, Gastrointestinal Oncology, Amsterdam, The Netherlands 4 The Netherlands Cancer Institute, Surgical Oncology, Amsterdam, The Netherlands Purpose or Objective In gastric cancer treatment, patient compliance to postoperative (postop) chemo(radio)therapy (CRT) is poor. Following the results of the recent CRITICS-I trial, as in other larger studies, only about 50% of patients completed adjuvant treatment as planned. Because preoperative (preop) therapies are better tolerated and associated with tumor downsizing, there is a rationale to shift from postop to preop strategies. The CRITICS-II trial aims to identify the optimal preop regimen: chemotherapy (CT), CRT or a combination. In the preop setting the stomach and regional lymph nodes are in situ without surgery-induced anatomical deformations. Due to the superior soft-tissue contrast of MRI, its integration in preop radiotherapy planning, allows a more accurate definition of the clinical target volume (CTV) and its margins. To evaluate MRI-based target delineation in gastric cancer, we undertook this feasibility study. Here, the first results of preop versus postop MRI-based CTV delineation in gastric cancer are reported. Material and Methods Patients with resectable gastric cancer underwent 2 MRI exams on a 3T Ingenia MRI (Philips Healthcare, Best, The Netherlands). The first MRI was scheduled before gastrectomy and start of neo-adjuvant therapy. The second MRI was scheduled 4-10 weeks after gastrectomy but before postop therapy. The MRI protocol consisted of axial and coronal T2-weighted (T2w) turbo spin echo (TSE) with navigator triggering, mDixon with breath hold, DWI and dynamic T1w 3D thrive during intravenous injection of 15ml gadolinium (Dotarem 0.5mmol/ml, Guerbet, France). Two radiation oncologists and a radiologist reviewed the image quality of the scans. Delineation of the CTV was done by a radiation oncologist (RO) and reviewed by a second RO. For comparison the volumes of the CTVs were determined in Mirada (Mirada Medical Ltd, Oxford, UK). Results Preop data from 7 evaluable patients were available for qualitative image analysis. The 3 reviewers concluded by visual inspection that axial T2wTSE with navigator triggering was most suitable for target delineation, due to the excellent contrast and limited motion artifacts. From 3 of the 7 patients the axial T2w TSE of both pre- and postop MRIs were available to delineate the CTV (Figure 1). CTVs in the preoperative setting were significantly larger than those in the postoperative (Table 1).

Conclusion For medium-sized HCC, there were no statistical differences in local control and OS between the SBRT and TACE groups. ECOG performance status was the only predictor for OS. EP-1438 Conventional radiotherapy combined with Stereotactic Body Radiotherapy boost for pancreatic cancer Y. Cha 1 , M.S. Kim 1 , Y.S. Seo 1 , C.K. Cho 1 , H.J. Yoo 1 , W.I. Jang 1 , E.K. Paik 1 , H.K. Jeong 1 1 Korea Institute of Radiological & Medical Sciences, Department of Radiation Oncology, Seoul, Korea Republic of Purpose or Objective To investigate the clinical application of a stereotactic body radiation therapy (SBRT) boost in locally advanced pancreatic cancer patients with a focus on local efficacy and toxicity. Material and Methods We retrospectively reviewed 47 patients with locally advanced and nonmetastatic pancreatic cancer who had been treated between 2004 and 2016. Follow-up duration ranged from 4 to 47 months (median, 14 months). A total dose of 40 Gy was delivered in 20 fractions using a conventional three-field technique, and then a single fraction of 10, 14, 15, 16, or 17 Gy SBRT was administered as a boost without a break. forty-one patients received chemotherapy. Overall and local progression-free survival were calculated and prognostic factors were evaluated. Results One-year overall survival and local progression-free survival rates were 57.0% and 73.0%, respectively. Three patients (6%) developed Grade 3 or higher toxicity. Tumor location and carbohydrate antigen 19-9 response was found to be an independent prognostic factor for survival. Conclusion Our findings indicate that a SBRT boost provides a safe means of increasing radiation dose. Based on the results