S727
Clinical – Lower GI
ESTRO 2026
2 Department of General Surgery, Peking Union Medical College Hospital, Beijing, China. 3 Department of Colorectal Surgery, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China. 4 Department of General Surgery, The First Affiliated Hospital of Jilin University, Jilin, China. 5 Fujian Medical University, Fujian Cancer Hospital, Fuzhou, China. 6 Department of Gastrointestinal Surgery, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China. 7 Department of Colorectal Surgery, Fudan University Shanghai Cancer Center, Shanghai, China Purpose/Objective: For early low-lying rectal cancer, neoadjuvant chemoradiotherapy (nCRT) plays a crucial role in facilitating organ preservation (OP) and sparing permanent colostomy. Our previous TORCH-E trial suggested that short-course radiotherapy (SCRT) followed by chemoimmunotherapy enhances tumor regression and may enable OP through a “Watch and Wait” (WW) strategy in patients achieving a clinical complete response (cCR). This study aims to compare the efficacy and safety of SCRT followed by CAPOX and PD-1 inhibitor pembrolizumab versus long-course chemoradiotherapy (LCRT) followed by CAPOX in proficient mismatch repair or microsatellite stable (pMMR/MSS), early low rectal cancer. Material/Methods: This is a prospective, randomized, multicenter phase II clinical trial. 134 patients with cT1–3bN0–1M0 rectal cancer proven pMMR/MSS and located ≤ 5cm from the anal verge will be enrolled. Participants will be randomly assigned to either SCRT or LCRT arm in a 1:1 ratio. Patients in SCRT arm will receive SCRT (25 Gy/5 Fx), followed by four cycles of CAPOX chemotherapy and PD-1 inhibitor pembrolizumab. Patients in LCRT arm will receive LCRT (50 Gy/25 Fx) with concurrent oral capecitabine (825 mg/m ² twice daily on radiotherapy days), followed by two cycles of CAPOX chemotherapy. Good responders are eligible for WW or local excision (LE), total mesorectal excision (TME) will be recommended for poor responders or those with high-risk features post-LE. The primary endpoint is complete response (CR), including cCR with WW and pathological CR (pCR). Secondary endpoints include OP rate, adverse effects, and quality of life. Results: Up to November 2025, 101 patients were enrolled and 51 patients have completed the treatment (SCRT arm 24, LCRT arm 27). The median age was 57, 68.6% (35/51) were T3 or N1. Thirteen and twelve patients achieved cCR and adopted WW in SCRT and LCRT arms, respectively. pCR was observed in 6 patients (2 in LE and 4 in TME) in SCRT arm and 4 patients (0 in LE and 4 in TME) in LCRT arm. The overall CR rates were
Conclusion: This is the largest reported prospective cohort of acute side effects after SCRT with IMRT. It provides a benchmark for future rectal cancer trials and radiotherapy optimisation. Keywords: Rectal Cancer, Short-Course Radiotherapy
Poster Discussion 3594 Short-course radiotherapy followed by
Pembrolizumab plus chemotherapy versus long- course chemoradiotherapy in early low rectal cancer (TORCH-E2) Yajie Chen 1 , Yaqi Wang 1 , Hui Zhang 1 , Juefeng Wan 1 , Lijun Shen 1 , Yan Wang 1 , Wang Yang 1 , Menglong Zhou 1 , Ruiyan Wu 1 , Shujuan Zhou 1 , Guole Lin 2 , Qian Liu 3 , Quan Wang 4 , Jinluan Li 5 , Changqing Jing 6 , Sanjun Cai 7 , Fan Xia 1 , Xinxiang Li 7 , Zhen Zhang 1 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.
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