ESTRO 2022 - Abstract Book

S366

Abstract book

ESTRO 2022

Conclusion Using systematic evaluations the interdisciplinary team was able to identify and agree on sequence selection for H&N (T1) and lung (T2). This process will be used moving forward to future MRL indications (e.g., pancreas). Work continues outside the vendor provided workflow to further optimise imaging.

OC-0421 MR-Guided SBRT/Hypofractionated RT for Metastatic and Primary Ultracentral and Central Lung Lesions

M. Sandoval 1 , A. Sim 1 , M. Bhandari 1,1 , E. Wuthrick 1 , B. Perez 1 , T. Dilling 1 , G. Redler 1 , J. Andreozzi 1 , L. Nardella 1 , V. Feygelman 1 , K. Latifi 1 , S. Rosenberg 1

1 Moffitt Cancer Center, Radiation Oncology, Tampa, USA

Purpose or Objective Results from Nordic-HILUS study indicate high dose radiotherapy may be associated with unacceptable high-grade toxicity for ultracentral tumors. We hypothesized that MR-guided SBRT (MRgSBRT) or hypofractionated RT (MRgHRT) for metastatic and primary ultracentral and central lung lesions would have excellent local control and minimal toxicity. Materials and Methods Single institution retrospective review of patients with ultracentral (per HILUS) or central (per RTOG) lesions treated with MRgSBRT/MRgHRT with image-guided gating and/or adaptation. Survival was estimated using Kaplan-Meier and stratifications tested using log rank test. Associations between incidence of toxicities and other patient factors were tested using Mann Whitney U test for continuous variables and Kendall’s tau-b for categorical variables. Other statistics analyzed descriptively. Results Between 2/2019-3/2021, 29 patients were treated with MRgSBRT/MRgHRT (median age 66.2 years, range 32.3-80.7) with a median follow-up of 18.1 months (95% CI 14.7-21.5). Sixty-two percent (n=18) had lung metastases and the remainder had primary lung cancers. All patients had central lesions per RTOG and 86% (n=25) fit criteria for Group A per HILUS trial; median distance from the proximal bronchial tree (PBT) was 0 mm (interquartile range [IQR] 0-6.5mm). The median GTV/PTV volumes were 11.1cc (IQR 6.6-20.2) and 21.8cc (IQR 14.8-42.5), respectively. The median biologically equivalent dose (BED; α / β =10) was 105 Gy (range 75-151.2), with the most common schedule being 7.5 Gy x 8 fractions (45%, n=13). A majority (55%) had prior systemic therapy, 45% (n=13) had immunotherapy, 17% (n=5) had thoracic RT, and 17% (n=5) had concurrent therapy with MRgSBRT, with 2 patients getting SBRT to another area of the lungs. Eight patients (27%) underwent daily adaptation with a median of 94% of fractions adapted (range 75-100%). Adaptive treatment course was shorter than non-adaptive (median 9 v. 13 days, p=0.013) and trended towards higher BED (105 Gy v. 100 Gy, p=0.053). Median OS was 24.8 months (95% CI 17.8-31.8), median PFS was 13.3 months (6.9-19.6), median LC was not reached. Five patients had pre-existing cough or dyspnea. No Grade 4 or 5 toxicities were seen. Single Grade 3 toxicity was esophagitis in one patient and persisted >3 months. Twelve Grade 1 toxicities and 8 Grade 2 toxicities were noted in 12 patients. No significant associations were found between toxicity and HILUS Group, BED, PBT distance, GTV/PTV volumes, prior therapies, concurrent therapy, or adaptive MRgRT. Conclusion Prior studies noted high rates of toxicity after SBRT to ultracentral/central lung lesions, with reports of Grade 5 toxicities. In our cohort, the use of MRgSBRT/MRgHRT with high BEDs resulted in excellent oncologic outcomes and a single Grade 3 toxicity with no Grade 4/5. Real-time image guidance, small treatment margins and adaptation afforded by MRI may expand the therapeutic window for ablative radiation in ultracentral/central lung lesions. M. Ejlsmark 1 , T. Schytte 1 , O. Hansen 2 , U. Bernchou 3 , A. Bertelsen 4 , S. Detlefsen 5 , M.B. Mortensen 6 , C.R. Hansen 7 , H. Jensen 8 , R. Bahij 8 , B. Weber 9 , P. Pfeiffer 10 1 Department of Clinical Research, University of Southern Denmark, Department of Oncology, Odense University Hospital , Odense, Denmark; 2 Department of Clinical Research, University of Southern Denmark, Department of Oncology, Odense University Hospital, Odense, Denmark; 3 Department of Clinical Research, University of Southern Denmark, Laboratory of Radiation Physics, Department of Oncology, Odense University Hospital, Odense , Denmark; 4 Laboratory of Radiation Physics, Department of Oncology, Odense University Hospital , Odense , Denmark; 5 Department of Clinical Research, University of Southern Denmark, Department of Pathology, Odense University Hospital, Odense , Denmark; 6 Department of Clinical Research, University of Southern Denmark, Department of Surgery, Odense University Hospital, Odense , Denmark; 7 Laboratory of Radiation Physics, Department of Oncology, Odense University Hospital, Odense, Denmark; 8 Odense University Hospital, Department of Oncology, Odense, Denmark; 9 Danish Centre for Particle Therapy, Department of Oncology, Aarhus University Hospital, Aarhus, Denmark; 10 Department of Clinical Research, University of Southern Denmark, Department of Oncology, Odense University Hospital, Odense , Denmark Purpose or Objective Stereotactic body radiotherapy (SBRT) has emerged as a promising new modality for locally advanced pancreatic cancer (LAPC). The current study evaluated the efficacy and toxicity of SBRT (planned 50 Gray in 5 fractions in 10 days) in patients with LAPC (NCT03648632). OC-0422 Adaptive MR guided stereotactic body radiotherapy for locally advanced pancreatic cancer