ESTRO 2025 - Abstract Book

S1775

Clinical – Upper GI

ESTRO 2025

exhalation BH, minimizing abdominal organ compression and enhancing BH reproducibility, in favor of optimal radiotherapy of abdominal cancer.

Keywords: deep-inspiration breath hold, abdomen radiotherapy

1613

Proffered Paper Randomised phase 2 study of preoperative chemo(radio)therapy in gastric cancer: preliminary results of the CRITICS-II trial Marcel Verheij 1,2 , Nicole CT van Grieken 3 , Shermarke Hassan 4 , Edwin PM Jansen 2 , Hanneke WM van Laarhoven 5 , Johanna van Sandick 6 , Evelien Schouten 4 , Romy M van Amelsfoort 2 , Astrid E Slagter 2 1 Radiation Oncology, Radboud University Medical Center, Nijmegen, Netherlands. 2 Radiation Oncology, Netherlands Cancer Institute, Amsterdam, Netherlands. 3 Pathology, Amsterdam UMC, Amsterdam, Netherlands. 4 Biometrics, Netherlands Cancer Institute, Amsterdam, Netherlands. 5 Medical Oncology, Amsterdam UMC, Amsterdam, Netherlands. 6 Surgical Oncology, Netherlands Cancer Institute, Amsterdam, Netherlands Purpose/Objective: From the CRITICS and other gastric cancer trials on multimodality treatment it is known that postoperative treatment is associated with poor patient tolerability. Therefore, CRITICS-II was designed to identify the optimal preoperative strategy, while omitting postoperative therapies. Here, we report preliminary results for the entire study population. Material/Methods: CRITICS-II (NCT02931890) is a randomised phase II trial evaluating 3 experimental preoperative treatment arms independently according to the “pick the winner” principle. Patients were randomised to: 4 cycles docetaxel/oxaliplatin/capecitabine (DOC); 2 cycles DOC followed by CRT (45 Gy with weekly carboplatin/paclitaxel; DOC-CRT); or CRT only. Primary endpoint is 1-year event-free survival. The trial has completed its intended inclusion and preliminary data are given for the entire group. Results: Between 2017 and March 2024, 207 patients were randomised; 206 were eligible for further evaluation. Median follow-up is 33.4 months. Completion of preoperative treatment for the total group was 77%. Main reasons for not completing preoperative treatment were toxicity (n=30), death (n=3), disease progression (n=1), patient’s refusal (n=5), or other (n=8). Surgery was performed in 90% of patients. Reasons for not proceeding to surgery were toxicity (n=7), disease progression (n=5), patient’s refusal (n=3), or other (n=5). Surgery with curative intent was performed in 99%, involving a total gastrectomy in 48% and a D2 lymph node dissection in 90%. In-hospital mortality was 4%. Surgical complications occurred in 19% and consisted of anastomotic leakage (n=14), ileus (n=8), bleeding (n=3), necrosis (n=2), wound dehiscence (n=2), fistula (n=1), and other (n=9). R0 resection was obtained in 95%; median number of lymph nodes was 25. The percentage of patients who completed treatment according to protocol was 70% for the total group. Maximum grade 3-5 any toxicity was 60%; grade 5 toxicity was 5%. Serious adverse event grade 3-5 was 26%. At present, 145 of 185 (78%) resection specimens have been centrally reviewed; a pathologic complete response of the primary tumor (TRG1) was found in 14%. At the current follow-up, 1-year event-free and overall survival are 75.3% (95% CI: 69.3%-81.8%) and 81.6% (95% CI: 76.1%-87.4%), respectively. Conclusion: In the CRITICS-II gastric cancer trial, where chemo(radio)therapy was entirely given prior to surgery, compliance rate was high (77% for the preoperative treatment; 70% for the full protocol). Treatment-related toxicity and surgical morbidity were significant, but in line with previous studies. Results regarding the primary endpoint are expected in 2025. Comparative analyses between the 3 treatment arms await mature follow-up.