Abstract 349P
Background
The aim of this prospective observational study is to evaluate the effectiveness of stereotactic MR-guided radiotherapy (MRgRT) for inoperable ductal pancreatic adenocarcinoma (PDAC) across various clinical scenarios.
Methods
Data from PDAC patients who received a 5-fraction MRgRT with a 0.35T system between April 2020 and October 2023 were captured from an institutional database. Overall survival (OS), local control (LC), and progression-free survival (PFS) were calculated using Kaplan-Meier Method. Therapy-associated side effects were classified according to CTCAE v5.
Results
53 consecutive patients were analyzed, with varying disease presentations, including synchronous metastatic (43%), locally advanced (LAPC) (28%), isolated local recurrence (ILR) (21%), and medically inoperable cases (7%). Induction chemotherapy was given to 78% of metastatic and 93% of LAPC patients, mainly using FOLFIRINOX (66% and 78%) for 7 and 4 months, respectively. Only 27% of ILR and 25% of medically inoperable patients received chemotherapy before MRgRT. The median CA19-9 value before MRgRT was 115 U/mL. The median prescribed dose was 40 Gy (range 33-40) with a corresponding biologically effective dose (BED10) of 72 Gy. Median follow-up from MRgRT was 11 months. LC rates were 92% and 80% at 6 and 12 months. Median OS post-MRgRT was 13 months, and 28 months from diagnosis. 1-year OS was 54%. Median PFS was 5 months. Notably, metastatic patients had a median OS of 13 months post-MRgRT, varying by disease state (17 months with stable disease, 10 months with progressive disease). LAPC and ILR patients had median OS of 13 and 16 months, respectively, with about 24% LAPC patients undergoing R0 resection. Medically inoperable patients had a 7-month median OS. The incidence of acute and late grade ≥3 side effects, possibly attributed to MRgRT, was limited to 2% and 6%, respectively.
Conclusions
MRgRT offers encouraging OS and LC rates with an acceptable toxicity profile in patients with unresectable PDAC, emphasizing its potential across different disease stages. Especially for the subset of metastatic patients with stable disease after exhaustion of first-line chemotherapy, MRgRT is a promising option. Further research and longer-term follow-ups are warranted.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.