ESTRO 2024 - Abstract Book

S1868

Clinical - Mixed sites, palliation

ESTRO 2024

respectively. Median PTV D 95 , D 90 , and D 80 were 40.0 Gy (IQR 31.9-50.0), 41.4 Gy (IQR 34.7-51.1), and 44.8 Gy (IQR 36.4-52.8), respectively.

With a median follow-up of 16.6 months post-MRgRT, acute grade 2 toxicities occurred in 28 (10.7%), while 2 (0.8%, abdominopelvic lymph nodes [n=2]) patients experienced grade 3 toxicities including bone pain (n=1) and diarrhea (n=1). Eight (3.1%) patients experienced late grade 2 toxicities with 3 (1.1%, abdominopelvic lymph nodes [n=2], and liver [n=1]) patients developing grade 3 toxicities, including constipation (n=1), bone pain (n=1), and diarrhea (n=1). Concurrent chemotherapy was administered to 71 (27.1%) patients; no differences in Grade 2+ toxicities were observed in those receiving concurrent systemic therapy or those treated with SBRT alone (15.5% vs. 12.0%, p=0.435). The rates of Grade 2+ toxicities at 1 and 2 years were 10.1% (95% confidence interval [CI], 6.4% to 13.8%) and 10.8% (95% CI, 6.9% to 14.7%), respectively. The 1- and 2-year rates of Grade 3+ toxicities were 1.3% (95% CI, - 0.3% to 2.9%) and 2.2% (95% CI, 0.0% to 4.4%). No patients experienced any acute or late grade 4+ toxicities.

Conclusion:

To our knowledge, this is one of the largest studies of MRgRT for oligometastatic disease to date and demonstrates that ablative dose can be safely delivered in 1-6 fractions to extracranial oligometastatic lesions. A remarkably low rate of grade 3+ toxicity was achieved without the need to significantly undercover the GTV and PTV at the prescribed dose. Ablative UHFx MRgRT for oligometastatic, oligoprogressive, and oligoresidual disease is feasible and well-tolerated even for lesions in unfavorable locations close to critical OARs.

Keywords: Ultra-Hypofractionation, MRgRT, Oligometastases

942

Mini-Oral

Decision regret after radiotherapy – A cross-sectional study in a broad spectrum of cancer patients

Alexander Rühle 1,2 , Leonie Wieland 1 , Andreas Hinz 3,2 , Anja Mehnert-Theuerkauf 3,2 , Clemens Seidel 1,2 , Nils H Nicolay 1,2

1 University of Leipzig Medical Center, Department of Radiation Oncology, Leipzig, Germany. 2 Cancer Center Central Germany, Partner Site Leipzig, Leipzig, Germany. 3 University of Leipzig, Department of Medical Psychology and Medical Sociology, Leipzig, Germany

Purpose/Objective:

The decision-making process regarding cancer treatment is a complex and emotionally challenging experience for patients and their families. Decision regret is a common yet underexplored aspect of this process, with potential long-term implications on patient well-being and satisfaction. This cross-sectional study aimed to investigate the prevalence and determinants of decision regret after radiotherapy in order to gain important insights into improving the shared decision-making process and enhancing support and guidance offered to patients during their radiation treatment.