Transition of Online Adaptive Stereotactic Radiotherapy for Pancreatic Cancer From Magnetic Resonance-Guided Linear Accelerator (MR-Linac) to State-of-the-Art Cone-Beam Computed Tomography (CBCT).

Pancreatic cancer is one of the most challenging tumor sites to treat safely and effectively with radiotherapy due to the anatomical location and aggressiveness of the disease. One modality that has shown promising results, which our institution has been employing, is online adaptive stereotactic radiotherapy using a magnetic resonance-guided linear accelerator (MR-linac). However, due to unforeseen circumstances regarding our MR-linac, it was necessary for our institution to use an alternative treatment technique. In this case report, we describe our experience using our ring-gantry linac equipped with an advanced cone-beam computed tomography (CBCT) system to treat a 61-year-old patient with advanced pancreatic cancer with CBCT-guided online adaptive stereotactic radiotherapy. In a short time period of four weeks, we prepared for this case by training with the surface scanning motion management system and developing procedures for planning and adaptation. The patient was prescribed 24 Gy in three fractions, with a risk-adapted approach using strict organ-at-risk (OAR) constraints. Daily CBCT was used for online adaptation of the plan, and the superior plan (non-adapted or adapted) was selected for treatment. For this patient, the adapted plan was chosen for all three fractions, due to OAR constraints being violated in the non-adapted plan. In summary, we found that for this patient, high-quality CBCT guidance for daily re-contouring, in combination with motion management, enabled the use of daily adaptive radiotherapy to safely deliver stereotactic radiotherapy. The results from this case report are promising, and CBCT-guided online adaptive stereotactic radiotherapy for pancreatic cancer warrants further investigation in more patients.

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Déclaration de conflit d'intérêts

Human subjects: Consent was obtained or waived by all participants in this study. Den Videnskabsetiske Komité issued approval H-19075387. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: Laura Rechner declare(s) a grant from Varian, a Siemens Healthineers Company. Laura Rechner is partially funded through a grant from Varian for work unrelated to this case report. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.