ESTRO 2025 - Abstract Book

S1169

Clinical – Lower GI

ESTRO 2025

Hillingdon Hospitals NHS Foundation Trust, Northwood, United Kingdom. 9 Mount Vernon Cancer Hospital, The Hillingdon Hospitals NHS Foundation Trust, Northwood, United Kingdom

Purpose/Objective: Squamous cell carcinoma of the anus (SCCA) is rare but increasing in incidence over the last 30 years. Patients with locally advanced disease are treated with radical intent with radiotherapy and chemotherapy but have a 1 in 3 chance of local failure or metastatic disease at 3 years. Immune checkpoint inhibition has recently been shown to be effective in the first line metastatic setting in combination with carboplatin and paclitaxel. CORINTH evaluates the addition of checkpoint inhibitor pembrolizumab to Intensity Modulated RadioTherapy with Chemotherapy (IMCRT) to improve Progression-Free Survival (PFS) and Overall Survival (OS) for high risk SCCA patients. Material/Methods: CORINTH is a multicentre, single arm, open-label, non-randomised study to evaluate the safety and tolerability of pembrolizumab with standard IMCRT (53.2Gy in 28d), with Mitomycin-C (D1) and Capecitabine (D1-28) in 50 patients aged 18 years or over with locally advanced SCCA and ECOG performance status 0 or 1. Pembrolizumab (200mg every 21d) was administered starting Day 1 Week 5 of the IMCRT schedule in Cohort 1 (Co1) and on Day 1 Week 1 in Cohort 2 (Co2). In both cohorts, pembrolizumab continued for 6 months (8 doses in total). Co1 and Co2 safety and toxicity data were reviewed by the Safety Review Committee (SRC). Primary endpoint was safety and tolerability, as assessed by adverse events (AE) and protocol adherence. Secondary endpoints include feasibility, overall response rate at 3, 6 and 12 months, and patient reported outcomes using EORTC quality of life questionnaires (EORTC QLQ C30, EORTC QLQ-ANL27). Results: Between March 2021 and July 2023, 13 patients were enrolled: 7 in Co1 and 6 in Co2. At the time of the safety review, 1 participant in Co1 withdrew for disease progression and one in Co2 at the Investigator’s decision due to toxicity. No treatment-related adverse events (TRAEs) were reported in Co1. Two patients in Co2 experienced TRAEs (all Grade 3), which included diarrhoea, hyperglycaemia, decreased lymphocyte count, oral mucositis, and vomiting. No deaths, either related to treatment or in the safety follow up, were reported. Conclusion: Initial findings suggest the introduction of pembrolizumab on Week 5 of IMCRT schedule (Cohort 1) or on Week 1 (Cohort 2) is safe. Recruitment has commenced to the expansion cohort of 38 patients to confirm safety and tolerability of pembrolizumab starting on Day 1 Week 1 of IMCRT schedule. This will provide data on relative efficacy against historical data. Registration: NCT04046133. Sponsor: Cardiff University

Keywords: SCC anus, Pembrolizumab, Phase 1b trial

1481

Mini-Oral Results of a phase II study of total neoadjuvant therapy for locally advanced rectal cancer(ClinicalTrials.gov No.: NCT04543695) Huiying Ma 1 , Yuan Tang 1 , Wenjue Zhang 2 , Haitao Zhou 3 , Zheng Liu 3 , Haizeng Zhang 3 , Yong Cai 4 , Yongheng Li 4 , Lichun Wei 5 , Shixin Liu 6 , Wenling Wang 7 , Hui Fang 1 , Yongwen Song 1 , Bo Chen 1 , Ningning Lu 1 , Hao Jing 1 , Shunan Qi 1 , Wenwen Zhang 1 , Xin Liu 1 , Yueping Liu 1 , Shulian Wang 1 , Xishan Wang 3 , Ye-xiong Li 1 , Jing Jin 2,1 1 Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), Beijing, China. 2 Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College