S704
Clinical – Lower GI
ESTRO 2026
Aalborg, Denmark. 7 Department of Clinical Medicine, Aalborg University, Aalborg, Denmark. 8 Department of Surgery, University Hospital of Southern Denmark, Vejle, Denmark. 9 Institute of Regional Health Research, , University of Southern Denmark, Odense, Denmark. 10 Department of Oncology, Aalborg University Hospital, Aarhus, Denmark
Purpose/Objective: Reirradiation for anal cancer recurrences is
constrained by prior high-dose exposure to pelvic organs of interest. Only a few, retrospective, studies have explored reirradiation with doses around 40Gy (1-4). The ongoing prospective phase II trial (ReRad III/DACG V) evaluates whether dose-escalated intensity-modulated proton therapy (IMPT) can be delivered as neoadjuvant or definitive treatment for recurrent anal cancer with acceptable rates of adverse events. We report 1-year adverse events and clinical outcomes for the first fifteen patients. Material/Methods: Fifteen patients with recurrent anal cancer (11 females/4 males) underwent IMPT reirradiation: neoadjuvant 55 Gy(RBE) in 44 fractions (n=3) or definitive 57.5–65 Gy(RBE) in 46–52 fractions (n=12).Status of the reirradiated recurrence at 12 months was assessed by MRI (n=13) or FDG-PET-CT (n=2). Given post-radiation changes, MRI reports describing fibrotic scars were classified as complete response (CR). Adverse events were scored per CTCAE v5.0. We report related or possibly related grade ≥ 3 events at 3, 6, and 12 months. Results:
Conclusion: The presence of baseline radiological EMVI and elevated NLR are independently associated with reduced odds of CR to TNT in our patient population. This correlation requires validation in a larger cohort. References: 1Audisio A,Gallio C,Velenik V et al. Total Neoadjuvant Therapy for Locally Advanced Rectal Cancer.JAMAOncol.2025;11(9):10452Zafari N,Khosravi F,Rezaee Z et al. The role of the tumor microenvironment in colorectal cancer and the potential therapeutic approaches.JClinLabAnal.2022;36(8):e245853Pine J,Morris E,Hutchins G et al. Systemic neutrophil-to- lymphocyte ratio in colorectal cancer: the relationship to patient survival, tumour biology and local lymphocytic response to tumour.BJC,2015;113,p2044Thompson H,Bates D,Pernicka J et al. MRI assessment of extramural venous invasion before and after total neoadjuvant therapy for locally advanced rectal cancer and its
association with disease-free and overall survival.AnnSurgOncol,2023;30,p3957 Keywords: Rectal, TNT, response
Proffered Paper 2211 The ReRad III trial: One-year efficacy, adverse events and feasibility of reirradiation for recurrent Anal Cancer (NCT05055635). Camilla J S Kronborg 1,2 , Bodil G Pedersen 3,2 , Heidi S Rønde 1 , Jesper F Kallehauge 1 , Eva Serup-Hansen 4 , Birgitte M Havelunde 5 , Lars Fokdal 5 , Lene H Iversen 6,7 , Jonas A Funder 8,9 , Mette M Sørensen 8,9 , Karen-Lise G Spindler 10,2 1 Danish Centre for Particle Therapy, Aarhus University hospital, Aarhus, Denmark. 2 Department of Clinical Medicine, Aarhus University, Aarhus, Denmark. 3 Department of Radiology, Aarhus University hospital, Aarhus, Denmark. 4 Department of Oncology, Copenhagen University Hospital, Herlev, Denmark. 5 Department of Oncology, University Hospital of Southern Denmark, Vejle, Denmark. 6 Department of Gastrointestinal Surgery, Aalborg University Hospital,
Median age was 64 years (range 49–78). Median interval from prior pelvic radiotherapy was 4.0 years
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