ESTRO 2023 - Abstract Book

S686

Monday 15 May 2023

ESTRO 2023

Conclusion SBRT used in the management of the oligometastatic gynaecological cancer led to good results in terms of local control with acceptable toxicity. Distant progression remains the primary site of failure in this setting.

PD-0814 Toxicity outcomes of dose-escalated MR-guided radiation therapy for abdominal and pelvic tumors R. Herrera 1 , T. Kutuk 2 , M. Chuong 2 , K. Mittauer 2 , M. Tom 2 , J. Contreras 2 , A. Kaiser 2 , M. Hall 2 , J. McCulloch 2 , D. Alvarez 2 , M. Mehta 2 , A. Gutierrez 2 , R. Kotecha 2 1 Miami Cancer Institute, Radiation Onocology, Miami, USA; 2 Miami Cancer Institute, Radiation Oncology, Miami, USA Purpose or Objective Magnetic Resonance Image-guided Radiation Therapy (MRgRT) offers improved soft tissue visualization compared to CT- based techniques, intra-fraction real-time fiducial-free tracking, and ability to adapt the treatment plan, facilitating dose- escalated radiotherapy (RT) for abdominal and pelvic tumors. In this study, we report our institutional MRgRT toxicity results. Materials and Methods Consecutive patients treated on a 0.35T MR-linac for primary and metastatic tumors in the abdomen and pelvis from April 2018 to September 2022 were evaluated. All were treated without fiducial markers and with real-time MR-based soft tissue tracking and automated beam gating, allowing for intra- and inter-fraction visualization of both the target and the critical organs-at-risk (OARs). The biologic effective dose with α / β of 10 Gy (BED10) was calculated for each treatment. The Common Terminology Criteria for Adverse Events (CTCAE) v5.0 criteria was used to score treatment-related toxicities by the treating physicians. Any toxicity within the first 3 months from completion of MRgRT was scored as “acute” and thereafter was scored as “late.” Results 335 patients with a median age of 68 years (range, 28-94) met the inclusion criteria. The most common treatment sites were pancreas (n=157, 47%), abdominopelvic lymph nodes (LNs) (n=70, 21%), adrenal glands (n= 48, 14%), and liver/hepatobiliary tract (n=44, 13%). All patients had ECOG 0-1 performance status. 208 (62%) patients were treated for