S702
Clinical – Lower GI
ESTRO 2026
Purpose/Objective: For mismatch repair proficient (pMMR) or
survivals. Results:
microsatellite stable (MSS) high-risk locally advanced rectal cancer (LARC, T3-4/N+M0), total neoadjuvant chemoradiotherapy (TNT) has been a preferred option. Recently, the combination of chemoradiotherapy and immunotherapy has shown enhanced tumor regression. However, there was a lack of evidence whether the addition of immunotherapy to TNT (iTNT) under a non-operative management (NOM)-prioritized strategy can lead to improved completer response (CR), organ preservation, and long-term survivals compared with TNT. This study aimed to compare differences in tumor response and long-term outcomes between iTNT and TNT. Material/Methods: This study retrospectively included 367 LARC patients treated from October 2009 to May 2023 at Fudan University Shanghai Cancer Center. Among them, 173 received iTNT regimen (short-course radiotherapy combined with CAPOX and Toripalimab), and 194 received TNT regimens (long-course chemoradiotherapy followed by double- or triple- agent chemotherapy: FOLFOX, CAPOX, CAPIRI, FOLFIRINOX, etc.). CR was defined as either pathological complete response after surgery or sustained clinical complete response (cCR) under watch-and-wait (W&W) management. Inverse probability of treatment weighting (IPTW) was used to adjust for baseline differences. Survival rates were calculated using IPTW-adjusted Kaplan–Meier curves. Results: The median follow-up was 27 months for iTNT group and 40 months for TNT group. After IPTW adjustment, the CR rate was significantly higher in iTNT group than TNT group (59.5% vs. 42.2%; OR = 2.008, P = 0.002). The iTNT group also showed significantly superior 2- year overall survival (OS) rate over TNT group (96.3% vs. 92.6%; HR = 0.38, P = 0.03). Among patients managed with W&W, the 2-year local regrowth rate was similar between iTNT and TNT groups (7.0% vs. 7.5%, P = 1.00), as well as the rate of 2-year sustained cCR survival (92.5% vs. 94.0%, P = 0.79). The iTNT group also showed numerically higher rate of 2-year disease free survival (81.4% vs. 77.3%, P = 0.34), lower rates of pelvic recurrence (4.5% vs. 8.8%, P = 0.14), total local failure (7.3% vs. 13.4%, P = 0.08) and distant metastasis (16.3% vs. 22.5%, P = 0.16) compared to the TNT group. Conclusion: The iTNT regimen yielded significantly higher CR rate and improved 2-year OS rate compared to TNT in LARC patients. iTNT represents a promising strategy for enhancing organ preservation and prolonging survival in patients with mid-low rectal cancer. Further validation through randomized large-sample clinical
1028 patients were analyzed. All patients received combined RCHT with (364) or without (664) a RT boost. The median OS was 12.8 years (range 0.5-16.2 years). The 5-year OS was 78.1%. RT boost correlated with an improved 5-year OS (81.3% versus 75.2%; p=0.050). In the predictive model, the single most important factor correlating with OS was pCR (base, importance 23.2%), followed by ypT1 (HR-1: 0.64, 95%CI 0.28-1.46), and ypT2 (HR-1: 0.58, 95%CI 0.33-1.01). The analysis for OS had a good discrimination with an AUC of 0.722 and a C-index of 0.718. The single most important factor that correlated with improved MFS was pCR (base, importance 30.2%), followed by having an ypT2 (HR-1: 0.51, 95%CI 0.3-0.88); ypT1 (HR-1: 0.42, 95%CI 0.21- 0.86), while factors correlated with a lower MFS were ypN2 (HR-1: 0.27, 95%CI 0.19-0.4), surgical margin (HR- 1:0.48, 95%CI 0.31-0.75), and ypN1 (HR-1: 0.57, 95%CI 0.41-0.8). The most important factors that correlated with improved DFS were: pCR, ypT2 and. We conducted a subgroup analysis in the “high-risk” population by including all patients cT3 cN1-2 or cT4 N-any. Globally, 366 patients in the standard dose and 188 in the RT boost were retrieved. The 3- and 5-year survival in the standard dose and RT boost were: OS (85% versus 88.2% and 74.6% versus 80.7%; p=0.03), MFS (72.1% versus 80.5% and 64.3% versus 77.5%; p=0.005), DFS (68.8% versus 78.7% and 59% versus 74.3%; p=0.001). Conclusion: The results of the present study contribute to enhance the role of pCR as a strong predictor of survival. Intensified RT might have an impact on survival, especially in patients with high-risk features and warrants prospective evaluation. Keywords: rectal cancer, neoadjuvant radiochemotherapy Comparison of Total Neoadjuvant Therapy with or without PD-1 blockade （ iTNT vs TNT ） for Locally Advanced Rectal Cancer Qianyu Zhou 1,2 , Yaqi Wang 1 , Luoxi He 1,2 , Zonglin Lv 1,2 , Zhiyuan Zhang 1 , Ruone Xu 1,2 , Hui Zhang 1 , Yajie Chen 1 , Menglong Zhou 1 , Wang Yang 1 , Jingwen Wang 1 , Ruiyan Wu 1 , Lijun Shen 1 , Juefeng Wan 1 , Shujuan Zhou 1 , Yan Wang 1 , Siyuan Chen 2 , Shuwen Li 1,2 , Fan Xia 1 , Zhen Zhang 1 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China. 2 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China Digital Poster Highlight 1821
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