S734
Clinical – Lower GI
ESTRO 2026
metastatic recurrences (23.7%), predominantly affecting the liver (55.6%) and peritoneum (22.2%), followed by lung (11.1%) and brain metastases (11.1%). Conclusion: Our study demonstrates that in patients with LARC treated according to the RAPIDO protocol, OS and DFS rates are encouraging, with a predominantly metastatic pattern of recurrence. No clinical factor analyzed (sex, age or tumor location) was significantly associated with survival outcomes. These findings suggest that longer follow-up and larger cohort studies are needed to better characterize prognostic factors and optimize management in this population. Keywords: rectal cancer, RAPIDO, survival prophylactic volumes in chemoradiotherapy in early anal squamous cell carcinoma – using data from PLATO-ACT4 Maxwell Robinson 1 , Natalie Abbott 2 , Christakis Agathokleous 3 , Rosie Cooke 3 , Francesca Fiorini 1 , Richard Eames 1 , Alexandra Gilbert 4,5 , Rebecca Johnson 6 , Rebecca Muirhead 6,7 1 Department of Radiotherapy Physics, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom. 2 National Radiotherapy Trials QA RTTQA Group, , Cardiff University Heath Park, Cardiff, United Kingdom. 3 Department of Radiotherapy, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom. 4 Leeds Cancer Research UK Clinical Trials Unit, Leeds Institute of Clinical Trials Research, Leeds, United Kingdom. 5 Leeds Institute of Medical Research at St James's St., St. James's University Hospital, Leeds, United Kingdom. 6 Department of Oncology, Oxford University Hospitals Digital Poster Highlight 4034 Assessing dosimetric benefit of reduced NHS Foundation Trust, Oxford, United Kingdom. 7 Department of Oncology, University of Oxford, Oxford, United Kingdom Purpose/Objective: The recently reported ACT4 trial (ISRCTN88455282) showed reduced dose radiotherapy does not compromise the 3-year disease free survival [1]. While it demonstrated improved acute toxicity, it did not significantly reduce late toxicity. An alternative strategy to address late toxicity, is to reduce elective treatment volumes as considered in the Nordic anal cancer (NOAC) group consensus guidelines [2]. We aim to use plans from ACT4 to quantify the dosimetric changes to organs at risk (OARs) with reduced elective treatment volumes Material/Methods: All ACT4 plans submitted for radiotherapy trial quality
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Clinical outcomes and survival after treatment of locally advanced rectal cancer according to the RAPIDO protocol Fatma Dhouib 1 , Yosra Kochlef 1 , Syrine Zouari 1 , Oumaima Bouabidi 1 , Eya Moalla 1 , Salah Boujelben 2 , Afef Khanfir 3 , Nejla Fourati 1 , Jamel Daoud 1 1 Oncology radiotherapy, Habib Bourguiba university hospital, SFAX, Tunisia. 2 General surgery, Habib Bourguiba university hospital, SFAX, Tunisia. 3 medical oncology, Habib Bourguiba university hospital, SFAX, Tunisia Purpose/Objective: The concept of Total Neoadjuvant Treatment (TNT) in locally advanced rectal cancer (LARC) has emerged to improve tumor control and treatment tolerance. The RAPIDO protocol was designed to enhance disease- free survival (DFS) and disease control in this high-risk population. This study aimed to evaluate DFS and overall survival (OS) and to identify potential prognostic factors in LARC patients treated according to the RAPIDO protocol. Material/Methods: A retrospective single-center study was conducted including patients treated for LARC according to the RAPIDO protocol between January 2020 and May 2023. All patients received short-course radiotherapy (5 × 5 Gy) followed by neoadjuvant chemotherapy (CAPOX or FOLFOX) prior to surgery. Clinical, pathological, and treatment data were extracted from medical records.The primary endpoints were overall survival (OS) and disease-free survival (DFS). Descriptive analysis of patient characteristics and survival analysis using the Kaplan-Meier method were performed. Results: Thirty-eight patients were included in this study with a sex ratio (M/F) of 1.2 and a median age of 60 years (range, 41–79). Tumor location was high rectum (13.2%), mid rectum (52.6%), and low rectum (34.2%). Most patients had T3 tumors (76.3%), followed by T4 tumors (23.7%), and regional lymph node involvement (N+) was observed in 94.7% of cases at diagnosis. The predominant histology type was adenocarcinoma of Lieberkühn (97.4%).The median follow-up was 25 months. The median OS was 68.4% and the 1-, 2-, and 3-year OS rates were of 78.9%, 70.8%, and 67.1%, respectively. No statistically significant association was found between OS and sex, age, or tumor location (p=0.725, 0.561, 0.428 respectively).The median DFS was 55.3% and the 1-, 2-, and 3-year DFS were of 60.5%, 57.9%, and 53.4%, respectively. DFS was not significantly associated with sex, age, or tumor site (p=0.193, 0.919, 0.316 respectively).Recurrences occurred in 31.6% of patients: 2 local recurrences (5.3%), 1 locoregional recurrence (2.6%), and 9
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