ESTRO 2025 - Abstract Book

S1215

Clinical – Lower GI

ESTRO 2025

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Poster Discussion SABR with fruquintinib and tislelizumab in metastatic colorectal cancer: Updated findings from a single arm, prospective phase II trial (RIFLE) Yajie Chen, Kun Wang, Hui Zhang, Wang Yang, Ruiyan Wu, Menglong Zhou, Zhen Zhang, Fan Xia Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China Purpose/Objective: Stereotactic ablative radiotherapy (SABR) has been shown to sensitize immunotherapy through inducing immunogenic death and remodeling the tumor immune microenvironment. Anti-angiogenic therapy exhibits synergistic antitumor effects with PD-1 antibodies through its immunomodulatory effects for metastatic colorectal cancer (mCRC) patients. Here, we report the updated findings from RIFLE trial: the efficacy and safety of the combination of fruquintinib, PD-1 inhibitor tislelizumab and SABR in mCRC patients. Material/Methods: RIFLE is a single-center, single-arm, prospective phase II clinical trial (NCT04948034). mCRC patients with at least 2 measurable lesions who have failed ≥ 1L standard therapy will receive SABR followed by fruquintinib (5 mg, d1-14, qd) and tislelizumab (200 mg, d1, q3w) within two weeks from completion of radiation. The primary endpoint is the objective response rate (ORR). The secondary endpoints include disease control rate (DCR), duration of response (DoR), progression-free survival (PFS) rate, overall survival (OS) rate and toxicity. Results: From August 2021 to November 2024, 46 patients were included in the trial and 41 in the efficacy analysis. Median age was 59 years, 28 (68.3%) patients were male, 35 (85.4%) had ≥ 3 metastases, and 21 (51.2%) had received ≥ 3 prior lines of systemic therapy. Median study follow-up was 19.2 months (95%CI:9.01-29.39), 1 patient achieved complete response (CR) for target lesions, 12 partial response (PR), 19 stable disease (SD), illustrating an ORR of 31.7% and a DCR of 78%. Median PFS was 9.2 months (95%CI:7.048-11.352). The most common treatment-related adverse events (TRAEs) were proteinuria (34.1%), hypertension (31.7%) and rash (19.5%). Grade 3-4 AEs occurred in 12 patients, including proteinuria and hypertension, and there were no treatment-related deaths. Conclusion: SABR combined with tislelizumab and fruquintinib shows promising effects and good safety in the treatment of metastatic colorectal cancer, which is expected to provide new therapeutic strategies and improve the prognosis for mCRC patients.

Keywords: mCRC, SABR, PD-1

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Mini-Oral Neoadjuvant Chemoradiotherapy with Simultaneous Integrated Boost for Stage II/III Rectal Adenocarcinoma: 9-year Outcomes of a Phase II Study Haoyue Li 1 , Yuan Tang 1 , Ning Li 1,2 , Ningning Lu 1 , Ningyu Wang 1 , Tongzhen Xu 1 , Hui Fang 1 , Yongwen Song 1 , Yueping Liu 1 , Bo Chen 1 , Shunan Qi 1 , Hao Jing 1 , Shulian Wang 1 , Yexiong Li 1 , Haitao Zhou 1 , Jing Jin 1,3 1 State Key Laboratory of Molecular Oncology and Department of Radiation Oncology, ational Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College (PUMC), Beijing, China. 2 Department of Radiobiology, Shanxi Province Cancer Hospital/ Shanxi Hospital Affiliated to Cancer Hospital, Chinese Academy of Medical Sciences/Cancer Hospital Affiliated to Shanxi Medical University, Taiyuan, China. 3 Department of Radiation Oncology, National Cancer Center /