S705
Clinical – Lower GI
ESTRO 2026
1 Department of Medical Oncology, University Medical Center Utrecht, Utrecht, Netherlands. 2 Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, Netherlands. 3 Department of Research and Development, Netherlands Comprehensive Cancer Organisation, Utrecht, Netherlands
(1.5–12.5). Recurrences were multifocal in 5 patients with a median diameter of 3.5 cm (1–8.2). Concurrent chemotherapy was cisplatin/capecitabine (n=8), cisplatin (n=2), or capecitabine (n=5), table 1.At 12 months, CR rate was 11/15 (73%) and PR 1/15 (7%). By 12 months 3 patients had progressed both local and distant. Three and 6 month response rates are also provided in table 1.In the neoadjuvant cohort (n=3): two CRs avoided surgery; one underwent R0 resection. In the definitive cohort (n=12): one patient proceeded to surgery with a pathologic CR. Related/possibly related grade ≥ 3 adverse events occurred in 2/15 (13%) at 3 months, 3/15 (20%) at 6 months, and 4/15 (26%) at 12 months. Including radiation dermatitis (n=2), pain (n=2), ileus (n=1), and deep venous thrombosis (n=1). One additional possibly related vertebral compression fracture was noted at 12 months. Conclusion: Dose-escalated proton reirradiation for recurrent anal cancer is feasible with high response rates and manageable severe adverse events at 1 year. Neoadjuvant IMPT enabled R0 resection or avoided surgery in all three patients, and definitive IMPT achieved durable CR in most patients by 12 months. These preliminary findings indicate that dose- escalated proton reirradiation may be considered as therapeutic option for recurrent anal cancer. Further enrollment and longer follow-up will clarify durability of control and late effects. References: 1. Osborne EMet al. Hyperfractionated Accelerated Reirradiation for Patients With Recurrent Anal Cancer Previously Treated With Definitive Chemoradiation. Am J Clin Oncol. 2018;41(7):632-7.2. Moningi Set al. Definitive hyperfractionated, accelerated proton reirradiation for patients with pelvic malignancies. Clin Transl Radiat Oncol. 2019;19:59-65.3. Hallemeier CLet al. Multimodality therapy including salvage surgical resection and intraoperative radiotherapy for patients with SCCA with residual or recurrent disease after primary chemoradiotherapy. Dis Colon Rectum. 2014;57(4):442-8.4. Damron EP et al. Salvage Treatment of Recurrent or Persistent SCCA: The Role of Multi-modality Therapy. Clin Colorectal Cancer 2024 Mar;23(1):85-94 Keywords: Reirradiation, anal cancer, proton therapy Digital Poster Highlight 2265 Advanced anal cancer: real-world patient, tumour and treatment characteristics Renee A Lunenberg 1 , Martijn P.W. Intven 2 , Femke P.C. Sijtsma 3 , Jeanine M.L. Roodhart 1 , Miriam Koopman 1 , Robert Jan J.M. Kwakman 1
Purpose/Objective: Advanced anal cancer is a rare disease, and
prospective trial data are scarce. Consequently, real- world evidence reflecting routine clinical practice is lacking. This large, nationwide cohort uniquely provides comprehensive insights into patient and tumour characteristics and current treatment patterns of patients with advanced anal cancer in the Netherlands. Material/Methods: This retrospective population-based cohort study of patients diagnosed between 2015 and 2023 used data from the Netherlands Cancer Registry. Baseline demographics, tumour characteristics, prior treatment history and management of advanced disease were analysed descriptively and stratified by disease presentation. Results: Among 301 included patients, 56 (19%) had locally recurrent inoperable disease, 116 (38%) had metachronous metastases, and 129 (43%) presented with synchronous metastases. At diagnosis of advanced disease, a third of patients were <60 years of age (31%). Females comprised 52% of the cohort, and 73% had a WHO performance status of 0-1. HPV status was available for 135 patients, of whom 73% were HPV-positive. Patients with metachronous metastases developed distant disease after a median of 14.2 months (IQR 8.0-24.3) from initial diagnosis and more often presented with multiple metastatic sites (55%) compared to those with synchronous metastases (31%). Of the 171 patients previously treated with curative intent, 80% had received chemoradiotherapy. Overall, 190 patients (63%) received treatment for advanced disease, while 111 (37%) received best supportive care only. Treatment approaches varied substantially across disease presentations. Patients with synchronous metastases most often received multimodal regimens, including chemoradiotherapy (23%) or systemic therapy and radiotherapy (17%). In contrast, those with metachronous metastases more frequently received systemic therapy alone (28%) or metastasis-directed therapy (27%), typically in sequential treatment setting. Patients with locally recurrent inoperable disease had the highest proportion without active treatment (63%). Detailed distributions of treatment types by disease presentation are shown in Table 1.
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