S1057
Clinical – Sarcoma, skin cancer, malignant melanoma
ESTRO 2026
Conclusion: RIS predominantly arise within high-dose irradiated regions and exhibit aggressive behaviour. Radical resection remains the cornerstone of curative management. Re-irradiation after surgery appeared associated with a trend toward improved local control, although limited by small sample size and potential confounders. Larger series are needed for more robust analyses to better understand tumor behavior, prognostic factors, and treatment response. References: 1. Kim JH, Chu FC, Woodard HQ, Melamed MR, Huvos A, Cantin J. Radiation-induced soft-tissue and bone sarcoma. Radiology. 1978 Nov;129(2):501-8. doi: 10.1148/129.2.501. PMID: 2799412. Callesen LB, Safwat A, Rose HK, Sørensen FB, Baad-Hansen T, Aggerholm-Pedersen N. Radiation-Induced Sarcoma: A Retrospective Population-Based Study Over 34 Years in a Single Institution. Clin Oncol (R Coll Radiol). 2021 May;33(5):e232-e238. doi: 10.1016/j.clon.2020.12.009. Epub 2020 Dec 30. PMID: 33386215.3. Spa ł ek MJ, Czarnecka AM, Rutkowski P. The Management of Radiation-Induced Sarcomas: A Cohort Analysis from a Sarcoma Tertiary Center. J Clin Med. 2021 Feb 10;10(4):694. doi: 10.3390/jcm10040694. PMID: 33578934; PMCID: PMC7916641. Keywords: sarcoma, radiation-induced Outcomes in Primary Meningeal Ewing’s Sarcoma (PMES): Retrospective analysis of the INSTINCT study Jifmi Jose Manjali 1 , Vaishnavi Pahawa 1 , Nehal Khanna 1 , Archya Dasgupta 1 , Abhishek Chatterjee 1 , Tejpal Gupta 1 , Poonam Panjwani 2 , Aekta Shah 2 , Ayushi Sahay 2 , Epari Sridhar 2 , Mukta Ramadwar 2 , Arpita Sahu 3 , Akshay Baheti 1 , Vasundhara Patil 4 , Venkata Rama Mohan Gollamudi 5 , Badira C P 5 , Sushmitha Rath 6 , Prabhat Bhargava 6 , Maya Prasad 5 , Girish Chinnaswamy 5 , Vikas Singh 7 , Prakash Shetty 7 , Aliasgar Moiyadi 7 , Siddhartha Laskar 1 1 Radiation Oncology, Tata Memorial Centre, Mumbai, India. 2 Pathology, Tata Memorial Centre, Mumbai, India. 3 RAdiology, Tata Memorial Centre, Mumbai, India. 4 RAdiology, Tata Memorial Centre, Mumabi, India. 5 Pediatric Oncology, Tata Memorial Centre, Mumbai, India. 6 Medical Oncology, Tata Memorial Centre, Mumbai, India. 7 Neurosurgery, Tata Memorial Centre, Mumbai, India Purpose/Objective: Primary Meningeal Ewing’s Sarcoma (PMES) is a rare diagnosis with limited literature. There is limited data on patterns of failure in PMES and the relevance of cranio-spinal irradiation (CSI) in the management of Digital Poster 5086
Instituto Português de Oncologia do Porto Francisco Gentil, Porto, Portugal. 3 Oncology, Instituto Português de Oncologia do Porto Francisco Gentil, Porto, Portugal. 4 Medical Physics, Instituto Português de Oncologia do Porto Francisco Gentil, Porto, Portugal. 5 Surgical Oncology, Instituto Português de Oncologia do Porto Francisco Gentil, Porto, Portugal Purpose/Objective: Radiation-induced sarcomas (RIS) are rare, aggressive malignancies that develop within previously irradiated fields. This study aimed to characterize their clinical and histopathological features and to evaluate treatment outcomes in a single reference center. Material/Methods: We retrospectively reviewed patients diagnosed with sarcoma between 2013 and 2022 who had received prior radiotherapy for another malignancy. Patients fulfilling criteria for RIS were included. Demographic, tumor-related, and treatment variables were collected. Patterns of recurrence and survival outcomes were analyzed. Results: Among 34 patients, 76.5% were female. The most common primary malignancies were breast (52.9%) and gynecological (11.8%) cancers. Median latency from radiotherapy to RIS diagnosis was 9 years (IQR 10.8), median age at diagnosis was 67 years (IQR 17) and median tumor size was 5.5 cm (IQR 5.9). RIS were most frequently located in the breast/trunk (58.8%) and pelvis (14.7%), with 82.4% arising within previously irradiated high-dose regions (>90% isodose).The predominant RIS histologies were angiosarcoma (35.3%) and undifferentiated sarcoma (35.3%). Aggressive histopathological features were common: 50% showed mitotic counts >20/10 HPF, 38.2% were histologically grade 3, and necrosis was observed in 38.2% of cases. Metastatic disease at diagnosis was present in 5.9% of patients.Curative-intent treatment was delivered in 70.6% of patients: 41.7% surgery alone, 25% surgery + radiotherapy, 16.7% surgery + systemic treatment + radiotherapy, 8.3% surgery + systemic treatment and 8.3% systemic therapy only, without proceeding to the planned surgical intervention.R0 margins were achieved in 70.8% of curatively treated cases. Median follow-up was 15 months (IQR 43.5). Loco-regional recurrence occurred in 35.3% and distant relapse in 26.5% (primarily lung, 66.7%).For patients treated with curative intent, 1-year and 3-year OS were 79.2% and 45.8%, respectively, with corresponding PFS rates of 54.2% and 41.7%.In the palliative-intent group, 1-year and 3-year OS were 50% and 20%, respectively, with PFS rates of 20% and 10%. In univariate Cox regression analysis of curative- intent treatments, radiotherapy showed a trend toward improved local control, although this did not reach statistical significance (HR 0.129, p= 0.056).
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