S718
Clinical – Lower GI
ESTRO 2026
10.2% (5/49) in chemotherapy group and 42.5% (17/40) in the radiotherapy group. The most common grade 3-4 adverse event (AE) among patients completing neoadjuvant treatment was thrombocytopenia, that 18.4% (9/49) in the chemotherapy group and 22.5% (9/40) in the radiotherapy group. Conclusion: The combination of PD-1 inhibitor, SCRT, and chemotherapy shows promising efficacy and may significantly improve pCR rates in patients with MSS/pMMR high-risk LACC. This regimen may provide a new therapeutic option to achieve R0 resection and improve long-term survival. Keywords: colon cancer, radiotherapy, immunotherapy Digital Poster Highlight 3106 Long-Term Oncologic and Patient-Reported Outcomes After IMRT-Based Chemoradiotherapy for Anal Canal Cancer: The PROACT Study. Viola De Luca 1 , Natalia Barogi 1 , Stefania Manfrida 1 , Diana Giannarelli 2 , Loredana Dinapoli 3 , Bruno Fionda 1 , Mirkia Moosavi 1 , Giuditta Chiloiro 1 , Daniela Pia Rosaria Chieffo 3,4 , Luca Tagliaferri 1 , Maria Antonietta Gambacorta 5 1 Radiation Oncology, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Roma, Italy. 2 Epidemiology and Biostatistics Facility, G-STeP Generator, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy. 3 Clinical Psychology Unit, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy. 4 Departement of Women, Children and Public Health, Università Cattolica del Sacro Cuore, Rome, Italy. 5 Università Cattolica del Sacro Cuore, Campus di Roma, Rome, Italy Purpose/Objective: Chemoradiotherapy (CRT) is the standard of care for squamous cell carcinoma of the anal canal (ACC), achieving excellent local control and sphincter preservation. However, many long-term survivors experience persistent bowel, urinary, and sexual dysfunctions that affect quality of life (QoL). The PROACT study (NCT06364579) investigated oncologic outcomes and patient-reported QoL in the era of modern IMRT-based CRT. Material/Methods: This single-institution ambispective study included 90 patients treated between 2011 and 2024 with IMRT- based CRT, followed—when indicated—by an image- guided interventional radiotherapy (IRT) boost. Oncologic outcomes and toxicity were assessed according to standard criteria. QoL was evaluated
Proffered Paper 3063
Neoadjuvant radiotherapy combined with CAPOX and PD-1 inhibitor for MSS/pMMR high-risk locally advanced colon cancer: a randomized phase Ⅱ Trial Hui Zhang 1 , Fan Xia 1 , Yaqi Li 2 , Wang Yang 1 , Yajie Chen 1 , Yaqi Wang 1 , Luoxi He 1 , Menglong Zhou 1 , Lijun Shen 1 , Yan Wang 1 , Juefeng Wan 1 , Ruiyan Wu 1 , Shujuan Zhou 1 , Jing Zhang 1 , Fangqi Liu 2 , Sanjun Cai 2 , Zhen Zhang 1 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China. 2 Department of Colorectal Surgery, Fudan University Shanghai Cancer Center, Shanghai, China Purpose/Objective: The prognosis for locally advanced colon cancer (LACC) with bulky nodal disease and/or clinically T4 stage remains poor, with high rate of recurrence and metastasis. Although neoadjuvant chemotherapy is recommended, tumor regression is often limited. Hypofractionated radiotherapy has demonstrated enhanced synergistic effects when combined with PD- 1 inhibitors and chemotherapy in rectal cancer. TORCH-C is the first prospective study evaluating neoadjuvant short course radiotherapy (SCRT) combined with chemotherapy and a PD-1 inhibitor in patients with microsatellite stable or mismatch-repair proficient (MSS/pMMR) LACC. Material/Methods: This is a prospective, multicenter, randomized phase II trial (NCT05732493). A total of 120 LACC (T4/bulky N+M0 ， pMMR/MSS) patients will be randomized to either a chemotherapy group or a radiotherapy group. The chemotherapy group receives 4 cycles of CAPOX. The radiotherapy group receives SCRT （ 25Gy in 5 fraction ） and 4 cycles of the PD-1 inhibitor (serplulimab) combined with CAPOX. The radiotherapy target volume includes only the primary colon tumor and enlarged lymph nodes, without elective nodal irradiation. After neoadjuvant therapy, patients will be evaluated for radical colon resection. The primary endpoint is pathological complete response (pCR) rate. The secondary endpoints include tumor downstaging, R0 resection, 3-year disease free survival (DFS), 3-year overall survival (OS), 3-year local recurrence-free survival and treatment-related toxicity. Results: As of October 31, 2025, 120 patients have been enrolled and randomized. Of these, 12 withdrew from the study, leaving 108 remaining. 100 patients have completed neoadjuvant treatment and 89 have received surgery (49 in the chemotherapy group, 40 in the radiotherapy group). All 89 patients achieved radical resection, with R0 resection rates of 95.9% (47/49) in the chemotherapy group, and 95.3% (38/40) in the radiotherapy group. The pCR rate (ypT0N0) was
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