S1056
Clinical – Sarcoma, skin cancer, malignant melanoma
ESTRO 2026
References: [1] Lansu J, Bovée JVMG, Braam P, van Boven H, Flucke U, Bonenkamp JJ, et al. Dose Reduction of Preoperative Radiotherapy in Myxoid Liposarcoma A Nonrandomized Controlled Trial. JAMA Oncol. 2021;7(1):1–8.[2] Kose ł a-Paterczyk H, Spa ł ek M, Borkowska A, Teterycz P, W ą grodzki M, SzumeraCie ć kiewicz A, et al. Hypofractionated Radiotherapy in Locally Advanced Myxoid Liposarcomas of Extremities or Trunk Wall: Results of a Single-Arm Prospective Clinical Trial. J Clin Med. 2020;9(8):2471. Keywords: myxoid liposarcoma, dose reduction, de- escalation The first reported series of 48 patients with late recurrence from Merkel cell carcinoma based on a 949-patient aggregated database Aoife Jones Thachuthara 1 , Kurian Joseph 2 , Edward YU 3 , Omar Alqaisi 4 , Ming Pan 5 , Suhair Al-Ghabeesh 4 , jidong lian 6 , vimal Prajapati 7 , Lorent Sijarina 8 , Mohammed Dibas 9 , Avi Assouline 10 , Michael Veness 11 , Patricia Tai 12 1 Medical oncology, Cork University Hospital of Prishtina, Cork, Ireland. 2 Radiation Oncology, Cross Cancer Center, Edmonton, Canada. 3 Radiation Oncology, London Cancer Program, London, Canada. 4 Nursing, Al-Zaytoonah University, Amman, Jordan. 5 Radiation Oncology, Windsor Cancer Center, Windsor, Canada. 6 Radiation Oncology, Trilium Health Partners, Mississauga, Canada. 7 Dermatology, Univesity of Calgary, Calgary, Canada. 8 Medical faculty, University of Prishtina, Prishtina, Canada. 9 Medicine, An-Najah National University, Neblus, Palestine. 10 Radiation Oncology, Collège de Médecine des Hôpitaux de Paris, Paris, France. 11 Radiation oncology, University of Sydney, Syndney, Australia. 12 Oncology, University of Saskatchewan, Saskatoon, Canada Purpose/Objective: Late recurrences of Merkel cell carcinoma (MCC)— defined as those occurring more than two years after initial treatment and remission—are rare but clinically important. While most MCC recurrences arise within 24 months, a subset of patients recurs years later, occasionally beyond five years. Few prior case reports have documented such late events, which challenge standard surveillance protocols and highlight the need Poster Discussion 4942 for extended follow-up. Another key question is whether MCC follows a cascade relapse pattern, progressing from local to nodal and then distant metastases for late recurrences. Material/Methods: An international research team compiled a comprehensive database of 949 patients: 303 were
treated at cancer centers in France, Canada, and Australia, while the remaining cases were extracted from published literature. A descriptive analysis was conducted. Results: Late recurrences were observed in 5.1% (48/949) of patients, involving local/nodal/distant/mixed sites. Median age at diagnosis was 70.8 years (range: 31–96), with a slight male predominance (58.3%). None of these patients were immunosuppressed. The median primary lesion size was 2 cm (range: 0.2–6).Of the 48 patients, 21 had lifetime local recurrence at a median time after initial presentation of 24 months (range 3- 96). Isolated lifetime nodal recurrence occurred in 8 patients at a median time of 47 months (range 27–48). Isolated distant recurrence was seen in 6 patients at a median time of 45.5 months (range 30–60).Among the 20 patients with both lifetime nodal and distant recurrences, nodal disease preceded distant spread by a median of 17 months (range: 0–40) and none had distant spread before nodal disease.Among the total 34 lifetime nodal recurrences (with or without local/distant recurrences), two patients survived without recurrence for >2 years. One of the two had extensive distant mediastinal and abdominal nodal recurrence at 60 months was salvaged with chemotherapy--6 cycles of CAV/EP (cyclophosphamide, adriamycin, vincristine/etoposide, cisplatin) and died cancer-free at 130.8 months. Conclusion: This is the first large-scale report on late MCC recurrence. The cascade pattern of spread (local- nodal-distant sites) was again observed in late recurrence, similar to other patient groups in the literature. Given the potential for late recurrence, extended surveillance by imaging and serologic monitoring beyond three years is recommended. Patient education is essential for early symptom reporting. Recognizing late recurrence enables timely intervention. As the current database reflects the pre- immunotherapy era, future expansion will incorporate immunotherapy data. Keywords: Merkel cell carcinoma, recurrence, database Radiation-induced sarcomas: clinicopathological patterns, treatment strategies, and survival outcomes from a single reference center Isabel Rocha Miguel 1 , Mariana Afonso 2 , Ana Magalhães Ferreira 3 , Miguel Henriques Abreu 3 , Fátima Borges 4 , Augusto Moreira 5 , Artur Aguiar 1 , Andreia Pires 1 , Sofia Conde 1 1 Radiation Oncology, Instituto Português de Oncologia do Porto Francisco Gentil, Porto, Portugal. 2 Pathology, Digital Poster 5017
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