ESTRO 36 Abstract Book

S224 ESTRO 36 _______________________________________________________________________________________________

Conclusion This is to our knowledge the largest series on SBRT in primary liver cancer reported. Local control is good in this cohort for both HCC and CCC with a moderate median BED, and median overall survival is well in the range of other series of SBRT in these entities. Prospective trials should be conducted to further validate the role of SBRT in primary liver tumors. OC-0425 Clinical experience with stereotactic MR- guided adaptive radiation therapy for pancreatic tumors A. Bruynzeel 1 , F. Lagerwaard 1 , O. Bohoudi 1 , S. Tetar 1 , N. Haasbeek 1 , S.S. Oei 1 , B. Slotman 1 , M. Meijerink 2 , S. Senan 1 , M. Palacios 1 1 VU University Medical Center, Radiation Oncology, Amsterdam, The Netherlands 2 VU University Medical Center, Radiology, Amsterdam, The Netherlands Purpose or Objective The duodenum is the primary dose-limiting organ when performing SBRT for locally advanced pancreatic cancer (LAPC). With technical and imaging advancements, the incidence of grade ≥3 small bowel toxicity (bleeding, perforation, strictures) has decreased to <10%, but potential toxicity continues to be a cause of concern. Stereotactic MR-guided adaptive radiation therapy (SMART) is a promising innovation, enabling besides daily plan adaptation, optimal and real-time normal tissue sparing while delivering high biological doses. The SMART approach was clinically implemented at our center in May 2016, using the MRIdian system (ViewRay). We report on SMART delivery in the first nine pts. Material and Methods SMART for LAPC is delivered in 5 fractions of 8 Gy (BED 10Gy 72 Gy), in two weeks on non-consecutive days, with prophylactic prescription of dexamethasone and ondansetron. Target (GTV) and organs-at-risk (OAR) contouring is performed on a MR-scan acquired at the MRIdian 0.35T during a 17 sec shallow inspiration breath- hold (BH). The GTV-PTV margin is 3mm, and the final PTV (PTV opt ) is created after subtraction of OAR within the initial PTV. A BH MR is repeated prior to each treatment fraction, and setup performed by GTV alignment. After contour deformation and adjusting OAR within 3 cm of the PTV opt , the original plan is re-optimized using the same number and direction of IMRT beams, to create a “plan of the day”. Patient specific QA includes an independent dose calculation step, followed by treatment delivered in BH periods under continuous MR-guidance. Respiratory- gating is performed using the GTV within the PTV opt , implying a 3mm safety boundary. BH is facilitated using an in-house developed video-feedback system, consisting of a mirror in the MR-bore and a monitor mounted at the head end of the MRIdian. Pts can observe in real-time the projected GTV within the PTV opt on a sagittal tracking image derived from the MRIdian console (Fig 1).

Proffered Papers: Upper and Lower GI

OC-0424 SBRT for Primary Liver Cancer in Routine Clinical Practice: A Patterns-of-Care and Outcome Analysis T. Brunner 1 , N. Andratschke 2 , S. Gerum 3 , N. Abbasi- Senger 4 , M. Duma 5 , O. Blanck 6 , V. Lewitzki 7 , C. Ostheimer 8 , F. Momm 9 , S. Wachter 10 , H. Alheit 11 , M. Guckenberger 2 , E. Gkika 1 1 Universitatsklinik Freiburg, Department of Radiation Oncology, Freiburg, Germany 2 University Hospital Zurich, Department of Radiation Oncology, Zurich, Switzerland 3 Ludwig-Maximilians-University, Department of Radiation Oncology, Munich, Germany 4 Friedrich-Schiller-University Jena, Department of Radiation Oncology, Jena, Germany 5 TU Munich- Klinikum Rechts der Isar, Department of Radiation Oncology, Munich, Germany 6 University Medical Center Schleswig-Holstein, Department for Radiation Oncology-, Kiel, Germany 7 University Würzburg, Department of Radiation Oncology, Würzburg, Germany 8 Martin Luther University Halle-Wittenberg, Department of Radiation Oncology, Halle an der Saale, Germany 9 Offenburg Hospital, Department of Radiation Oncology-, Offenburg, Germany 10 Klinikum Passau, Radiation Oncology, Passau, Germany 11 Strahlentherapie Bautzen, Radiation Oncology, Bautzen, Germany Purpose or Objective SBRT is not mapped on the treatment algorithms for primary liver tumors. We evaluated safety and efficacy of SBRT for primary liver cancer in a patterns-of-care and patterns-of-outcome analysis. Material and Methods The working group 'Stereotactic Radiotherapy” of the German Society for Radiation Oncology performed a retrospective multicenter analysis of SBRT for hepatocellular and cholangiocellular carcinoma (HCC and CCC). Eleven centers with experience in pulmonary SBRT participated. SBRT for this indication was introduced in 1999 and data were entered into a centralized database. The analysis comprised 206 lesions in 174 patients after retrieval of patient, tumor and treatment data from the aforementioned multi-center database. HCC and CCC were analyzed separately and pooled. Available factors were analysed for local control (LC), overall survival (OS) and toxicity. Results The range of lesions per center was 1–100 with a median of 13 patients per center. In 174 patients 206 lesions were treated, 134 (65%) HCC and 72 CCC lesions. Karnofsky Performance Status was 80-100 in 88% and 60-70 in 12%. Child-Turcotte-Pugh stage in HCC was A, B and C in 62%, 29% and 6%. Largest tumor diameter was median 5 cm (SD 3.9) with 144 patients having a single target lesion, 26 with 2, 3 with 3 and 1 with 4 lesions. PTV volume was median 127 cc (5 - 3553). Median BED 10 prescribed to the PTV margin was 72 Gy (range 36 - 180 Gy): SBRT was delivered in a median of 5 fractions (3-17) to a median PTV prescription dose of 45 Gy (30 - 68 Gy ). Median follow-up of patients alive was 12 months. Local control was 89%, 87% and 83% at 12, 18 and 24 months with no significant difference between HCC and CCC. Two-year LC was 81% vs. 91% (p = .075) for doses < 72Gy BED vs ≥ 72 Gy BED, respectively. Median OS was 16.7 months, 17.5 months and 14.6 months for HCC vs CCC (p=n.s.). Gastroduodenitis was grade 2 or 3 in 2% and 1%, respectively. Data on other toxicity was only available in 41% and was ≥ grade 2 in 4%: this was esophageal variceal bleeding grade 2 in 3 patients and deteriorated liver function in 3 patients.