ESTRO 2023 - Abstract Book

S1116

Digital Posters

ESTRO 2023

Conclusion Online adaptive MRgRT with a 1.5T MR-linac is feasible for pancreatic and peri-pancreatic tumors with limited adverse treatment effects and a stable QoL at three months FU. Furthermore, treatments could be delivered as planned, with low numbers of missed fractions.

PO-1386 Treatment outcomes of 1.5 T MR-guided adaptive radiotherapy for locally advanced pancreatic cancer

G. Yavas 1 , C. Yavas 1 , G. Arslan 1 , E. Efe 1 , C. Onal 1,2

1 Ba ş kent University, Radiation Oncology, Ankara, Turkey; 2 Baskent University Adana Dr. Turgut Noyan Research and Treatment Center, Radiation Oncology, Adana, Turkey Purpose or Objective Pancreatic cancer is still a devastating disease, with 30% of patients experiencing isolated loco-regional relapses. Novel multidrug combinations have improved clinical outcomes in patients with metastatic disease and are now being used more frequently in patients with locally advanced/localized disease. Because of its improved image quality, 1.5-Tesla magnetic resonance imaging-guided adaptive radiotherapy (MRgRT) allows for dose escalation for tumors while minimizing doses to healthy tissues. We aimed to assess preliminary results of locally advanced pancreatic cancer patients treated with 1.5T MR-LINAC Materials and Methods Eighteen patients with inoperable/borderline resectable or recurrent pancreatic cancer treated with 1.5T MRI-g-ART (Unity® MR Linac System, Elekta AB, Stockholm, Sweden) retrospectively evaluated. Twelve patients (67%) received neoadjuvant and adjuvant chemotherapy, while 6 patients (33%) were treated with adjuvant chemotherapy after MRgRT. The treatment details and early treatment results as well as the toxicity outcomes were reported. Results The average age was 64 years (range; 38–80 years). Eleven (61%) of the patients were female, while 7 (39%) were male. The primary tumor was located at head of pancreas in 16 patients (89%) and at corpus in two patients (11%). Except for those who received a second course of RT, the median prescribed dose was 33 Gy (range, 25–45 Gy) in 5 fractions for all patients. Except for those who received a second course of RT, the median prescribed dose for all patients was 33 Gy (range, 25-45 Gy) in 5 fractions. The average treatment time, including preparation, planning and administration, was 54 minutes (41–75 minutes). With a median follow-up time of 24.2 months (95% CI 20.3-28.1 months), 10 patients (56%) died as a result of disease progression, while 8 patients (44%) survived (6 patients with disease). Disease progression was seen in 13 patients (72%), all of whom had distant metastasis, while four had local recurrence with distant metastasis. One of the inoperable pancreatic cancer patients who was in excruciating pain received complete pain relief. Two of the three patients with borderline resectable pancreatic cancer underwent surgery. There were no cases of acute and late toxicity of grade 2 or higher. Conclusion MRgRT is a promising treatment option with lower toxicity rates for borderline resectable/unresectable/recurrent pancreatic cancer because it allows for patient-specific treatment planning and dose distribution. However, disease progression was observed in majority of patients as distant metastases, with only four patients experiencing recurrence at the MRgRT-treated lesion. This necessitated the use of an effective systemic therapy in order to improve treatment outcomes