ESTRO 2024 - Abstract Book

S2199

Clinical - Upper GI

ESTRO 2024

MR-Guided Stereotactic Radiotherapy for Advanced Pancreatic Cancer: Prospective Registry Study

Mohemed Shouman 1,2 , Aurélie Gaasch 1 , Sandra Boyaci 1 , Frederik Fuchs 1 , Maya Rottler 1 , Franziska Walter 1 , Sebastian Marschner 1,3 , Chukwuka Eze 1 , Maximilian Niyazi 4,5,1 , Claus Belka 1,2,3 , Stefanie Corradini 1 , Paul Rogowski 1 1 University Hospital LMU, Department of Radiation Oncology, Munich, Germany. 2 Bavarian Cancer Research Center (BZKF), Partner Site Munich, Munich, Germany. 3 German Cancer Consortium (DKTK), Partner Site Munich, Munich, Germany. 4 University Hospital Tübingen, Department of Radiation Oncology, Tübingen, Germany. 5 German Cancer Consortium (DKTK), Partner Site Tübingen, Tübingen, Germany

Purpose/Objective:

Stereotactic MR-guided Radiotherapy (MRgRT) is an emerging treatment modality for unresectable pancreatic ductal adenocarcinoma (PDAC). This prospective observational study investigates the outcomes of PDAC patients treated with MRgRT, encompassing various clinical scenarios where MRgRT might be advantageous for patients with unresectable PDAC.

Material/Methods:

A prospective institutional database collected data of PDAC patients treated with 5-fraction MRgRT using a 0.35T MR-guided radiation delivery system. Indications for treatment were determined in a multidisciplinary tumor board. Overall survival (OS), local control (LC), distant metastasis-free survival (DMFS), and progression-free survival (PFS) were calculated using the Kaplan-Meier method. Acute and late toxicities were graded according to CTCAE v5.

Results:

Fifty-five consecutive patients were analyzed. The median age was 69 years (43-90), and 67% had an ECOG score of 0-1. Patients had varying disease presentations, including synchronous metastatic (45%), locally advanced (LAPC) (24%), isolated local recurrence (ILR) (24%), and medically inoperable cases (7%). Induction chemotherapy was administered to 84% of metastatic and 92% of LAPC patients, with predominant usage of FOLFIRINOX (67% and 75%) and median treatment durations of 7 and 4 months, respectively. In the ILR group, only three patients (24%) received chemotherapy upon local relapse pre-MRgRT, whereas in the medically inoperable group, just one patient (25%) underwent chemotherapy. The median CA19-9 value before MRgRT was 103 U/mL, with the four groups having median values of 133, 147, 70, and 47 U/mL, respectively. The median prescribed dose was 40 Gy (range 25 40) with a corresponding biologically effective dose (BED10) of 72 Gy. The median follow-up from MRgRT and the date of diagnosis were 10 months and 23 months, respectively. The median OS and 1-year OS post-MRgRT were 14 months and 58%, respectively. The median OS from the time of diagnosis was 29 months. LC was 92 % and 81% at 6 and 12 months after MRgRT. Median PFS and median DMFS were five and six months, respectively. The incidence of acute and late grade ≥3 toxicity, possibly attributed to MRgRT, was limited to 5% and 4%, respectively. When stratified by disease stage, metastatic patients achieved a median OS and 1-year OS of 14 months and 56% after MRgRT. Patients with LAPC showed a 13-month median OS and 58% 1-year OS, while patients with ILR exhibited a 16-month median OS and 56% 1-year OS. Notably, 23% of the initial LAPC patients underwent surgical