ESTRO 2025 - Abstract Book

S1742

Clinical – Upper GI

ESTRO 2025

Post-surgical pathological assessment was performed based on College of American Pathologists(CAP) criteria, categorising the resection status as R0 (no residual disease), R1(positive, microscopic residual disease) and R2(positive, macroscopic residual disease). On the other hand, tumor response assessment was evaluated with the Tumor Response Scoring (TRS) system of the CAP, reported as , score 0 (no viable tumour cells), score 1 (single cells or rare small groups of cancer cells), score 2(residual cancer with evident tumor regression) and score 3 (extensive residual cancer with no evident tumor regression). Results: 33 patients (p) were included,13 p(39.4%) were BRPC and 20 p (60.6%) LAPC. After ChT-SABR, 12p (36,4%) became resectable, 2p(6,1%) continued as BRPC, 19 (57.6%) remained unresectable. 11p (33,3%) underwent surgery. Pathological outcomes were reported as resection status and TRS score. Resection status: 8 p(72.7%) R0, 3p (27.3%) R1, and none R2. TRS were score 1 in 27.3% (3p), score 2 in 54.5% (6p), and score 3 18.2% (2p). None patients achieve score 0. After a median follow-up of 19months (6 –71months), Recurrence rates were: 25 p(75,8%) distant recurrences, 12 p (36,4%) local recurrences and 5 p (15,2%) recurrence-free. FFLP-rates from SBRT 1-2years were 91,6%(95% CI:85,9-96%) and 79,3%(95% CI:79,3-85,9%), respectively (Figure 1) In a sub-analysis patients who received a BED >100, 92.9% (13/14p) became resectable compared to only 7.1% (1/14p) in the BED<100 (p = 0.026).

Conclusion: Neoadjuvant ChT-SABR in LAPC improves resectability rates and presents relevant tumor regression at scoring, enhancing local control. The escalated to ablative doses is associated with an evidently higher significant probability of achieving resectability in previous unresectable LAPC.

Keywords: LAPC, SABR, Escalated-Ablative-Dose

References: 1. Salas B, Ferrera-Alayón L, et al. Dose-escalated SBRT for borderline and locally advanced pancreatic cancer. Feasibility, safety and preliminary clinical results of a multicenter study. Clin Transl Radiat Oncol. 2024 Feb 23;45:100753. doi: 10.1016/j.ctro.2024.100753. 2.Comito T, Massaro M, et al. Can STEreotactic Body Radiation Therapy (SBRT) Improve the Prognosis of Unresectable Locally Advanced Pancreatic Cancer? Long-Term Clinical Outcomes, Toxicity and Prognostic Factors on 142 Patients (STEP Study). Curr Oncol. 2023 Jul 24;30(7):7073-7088. doi: 10.3390/curroncol30070513.