S1059
Clinical – Sarcoma, skin cancer, malignant melanoma
ESTRO 2026
patients and general practitioners. Existing literature, such as a PubMed analysis of 109 misdiagnosed cases, underscore the challenges in timely MCC diagnosis. This study aims to investigate the direct impact of patient-related delays for seeking medical opinion on clinical outcomes in MCC. Material/Methods: A detailed international database was complied, merging anonymous data from 303 MCC patients across Canda, France, and Australia with published individual patient data from an additional 646 cases. The combined databases comprised 949 patients. Descriptive and comparative analyses were performed, focusing on the time interval before patients sought medical opinion and subsequent disease stages at presentation, recurrence rates, and
survival. Results:
Among the 949 patients, quantifiable time interval before seeking medical evaluation was recorded in 322 (33.9%), with the median being 4 months (range 0- 60). Those presenting earlier (shorter than the median delay) and later (longer than the median delay) were compared for initial stages (localized, nodal, or metastatic), recurrence rates, and 5 years overall and cause-specific survival. Statistical analyses including chi-square and log-rank tests were applied. Results indicate that delayed presentation is associated with a trend for advanced-stages disease at diagnosis: 73.6% localized, 21.5% nodal and 3.5% distant disease, versus 82.5% localized, 14.7% nodal and 2.3% distant disease for those with < 4 mos (P=0.09, chi-square test). The rate of disease recurrence in any sites after treatment was 63.9% vs 62.1% (P=0.74, chi-square test). The 5-year overall survival rates were 30.2% versus 36.1% (P=0.37, log-rank test). The 5-year cause- specific survival rates were 51.6% versus 59.0% (P=0.47, log-rank test). Conclusion: Patient delay in seeking medical opinion in Merkel cell carcinoma may compromise outcomes by predisposing to advanced disease. Urgent strategies to reduce diagnostic delays-such as targeted patient education, improved clinical diagnostic protocols, and early use of biomarkers (e.g. MCC polyomavirus titre) – are crucial. Early multidisciplinary management may significantly improve survival in MCC. Keywords: Merkel cell carcinoma (MCC), outcome, delay
Conclusion: Postoperative radiotherapy with moderate dose- escalation appears to be a feasible and well-tolerated treatment option for patients with PTs at high risk of recurrence. While no relapses were observed, further studies with larger cohorts and longer follow-up are necessary to confirm these findings and optimize treatment strategies. Radiotherapy should be considered on a case-by-case basis, particularly for high-risk tumors with close or positive margins. Keywords: phyllodes tumor, local control, hypofractionation Digital Poster 5171 Merkel cell carcinoma: prevalence and impact of delayed presentation in an international aggregated 949-patient database Aoife J Thachuthara 1 , Omar Alqaisi 2 , Kurian Joseph 3 , Ming Pan 4 , Suhair Al-Ghabeesh 2 , Edward YU 4 , Patricia Tai 5 1 medical oncology, Cork Univ. Hosp., Cork, Ireland. 2 nursing, Al-Zaytoonah University, Amman, Jordan. 3 oncology, A. Alberta, Edmonton, Canada. 4 oncology, Western U., London, Canada. 5 oncology, U. Sask., Saskatoon, Canada Purpose/Objective: Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer predominantly affecting the elderly, who often delay seeking medical for asymptomatic lesions. Its clinical resemble to benign or less aggressive skin lesions frequently leads to diagnostic delays by both
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