ESTRO 2025 - Abstract Book

S1256

Clinical – Lower GI

ESTRO 2025

3848

Poster Discussion Outcomes after (chemo)radiotherapy for anal cancer – a nationwide cohort study

Charlotte L. Deijen 1,2 , M. Berbeé 3,4 , Elisabeth D. Geijsen 5 , Karen J. Neelis 6 , Leonard Wee 3,4 , Patty H. Spruit 1 , Marjolein A.B. Bakker-Van der Jagt 7 , Onne Reerink 8 , Heidi Rutten 9 , Karin Muller 10 , Jeltsje S. Cnossen 11 , Vera Oppedijk 12 , Tilly Leseman 13 , Anniek H. Boer 14 , Heleen M. Ceha 15 , Gati Mulder-Ebrahimi 16 , Martijn P.W. Intven 17 , Baukelien Van Triest 2 1 Radiation Oncology, Northwest Clinics, Alkmaar, Netherlands. 2 Radiation Oncology, NKI-AVL, Amsterdam, Netherlands. 3 Radiation Oncology, Maastro, Maastricht, Netherlands. 4 GROW Research Institute for Oncology and Reproduction, Maastricht University Medical Centre+, Maastricht, Netherlands. 5 Radiation Oncology, Amsterdam University Medical Centres, location AMC, Amsterdam, Netherlands. 6 Radiation Oncology, Leiden University Medical Centre, Leiden, Netherlands. 7 Radiation Oncology, Amsterdam University Medical Centres, location VUmc, Amsterdam, Netherlands. 8 Radiation Oncology, Isala Clinic, Zwolle, Netherlands. 9 Radiation Oncology, Radboud University Medical Center, Nijmegen, Netherlands. 10 Radiation Oncology, 9. Radiotherapy group, Deventer, Netherlands. 11 Radiation Oncology, Catharina Hospital, Eindhoven, Netherlands. 12 Radiation Oncology, Radiotherapy Institute Friesland, Leeuwarden, Netherlands. 13 Radiation Oncology, Zuidwest Radiotherapeutisch Instituut, Roosendaal, Netherlands. 14 Radiation Oncology, University Medical Centre Groningen, Groningen, Netherlands. 15 Radiation Oncology, Haaglanden Medical Centre, The Hague, Netherlands. 16 Radiation Oncology, Instituut Verbeeten, Tilburg, Netherlands. 17 Radiation Oncology, University Medical Centre Utrecht, Utrecht, Netherlands Purpose/Objective: Due to rarity of anal cancer, real-world data on treatment outcomes are historically scarce, however its incidence has been increasing in The Netherlands (>200 new patients and 50 deaths per annum) 1 . Standard of care consists of chemoradiotherapy (CRT) or radiotherapy alone (RT), aiming to preserve anal function without compromising local control. The primary objective of our nationwide retrospective chart study was two-fold; to evaluate real-world outcomes after curatively-intended CRT/RT for anal squamous cell carcinoma (ASCC), and to create a large high quality dataset as a national benchmark to guide future prospective research. Material/Methods: Data were assembled from patient chart reviews from 16 Dutch institutions treating ASCC between 2015 and 2018. Primary endpoint was locoregional recurrence free survival (LRFS). Secondary endpoints were complete response (CR), overall survival (OS), disease specific survival (DSS) and colostomy free survival (CFS). Data on treatment regimen, toxicities, prognostic risk factors, case-volume effects and palliative outcomes will be reported separately. Results: A total of 462 patients were analysed (Table 1). The median age was 63.5 years. The majority of tumours were staged T2 (51%), N0 (53%), and M0 (99%). HPV and/or p16 status was reported in 157 patients, out of which 124 patients were classified positive (79%). Most patients received CRT (85%), with mitomycin-capecitabine as a radiosensitizer in 73% of cases. After median follow-up of 5 years, LRFS for all patients was 79% at 3 years and 77% at 5 years (Figure 1). In total 82% of patients had reached CR, with a median interval to define CR of 3 months. Digital rectal examination was the most commonly-used CR assessment method (76%), followed by magnetic resonance imaging (37%). At 3 years, OS, DSS and CFS (Figure 2) rates for all patients were 78%, 86% and 88%, respectively. The estimated median OS time was 6.9 years; median had not yet been reached for LFRS, DSS nor CFS.