S1034
Clinical – Sarcoma, skin cancer, malignant melanoma
ESTRO 2026
invading beyond subcutaneous fat and immunosuppression were extracted with follow-up over 3-5 years performed assessing local/ locoregional recurrence, DSM and overall survival. Results: Sixty-six patients were analysed with follow-up of three to five years. See Table 1 for patient demographics, disease and ART details. HRFs were frequent, with tumour diameter >20mm in 71%, aggressive histology in 50%, perineural invasion in 48%, and thickness >6mm or invasion beyond subcutaneous fat in 89%. Immunosuppression was present in 27%. Table 2 shows the outcomes of our patient cohort. Despite ART, local recurrence occurred in 15% and locoregional recurrence in 24%. DSM was 12% and all-cause mortality 32%. Seventy-four percent of patients had either a surgical margin <1mm or recurrence (74%) and post ART had a local recurrence rate of 12%, locoregional recurrence of 22% and DSM of 14%. The remaining 26% of patients with clear margins and de novo disease had a local recurrence rate of 24%, locoregional recurrence rate of 29% and DSM of 6%. In this group, risk of local recurrence rose with number of HRFs – 0% with 2 HRFs up to 33% with 4 HRFs.Table 1. Patient demographics, disease and ART details
median follow-up of 14 months (range, 4–21), local control was 100%, with no distant metastases. Conclusion: Moderately hypofractionated preoperative RT (42.75 Gy in 15 fractions) of extremities and trunk STS demonstrated excellent tolerance, high pathologic response, and outstanding early local control, with a low rate of wound complications. These preliminary results support this schedule as a safe and efficient alternative to the conventional 50 Gy in 25 fractions regimen. Longer follow-up is warranted to confirm durability of local control and late side effects profile. References: 1. Haas RL, Floot BGJ, Scholten AN, et al. Cellular Radiosensitivity of Soft Tissue Sarcoma. Radiat Res. 2021;196:23–30.2. Kokkali S, Boukovinas I, de Bree E, et al. The Impact of Expert Pathology Review and Molecular Diagnostics on the Management of Sarcoma Patients: A Prospective Study of the Hellenic Group of Sarcomas and Rare Cancers. Cancers (Basel). 2024;16:2314. 3. Stergioula A, Kormas T, Kokkali S, et al. What Is the Prognostic Value of the Pathologic Response after Neoadjuvant Radiotherapy in Soft Tissue Sarcoma ? An Institutional Study Using the EORTC – STBSG Response Score. Cancers (Basel). 2024;16:3449. Keywords: preoperative radiotherapy, hypofractionation, STS Digital Poster 1636 Impact of high-risk factors on outcomes in cutaneous squamous cell carcinoma treated with adjuvant radiotherapy Cara Beattie, Charis R Thompson, Gordon Anderson, Heather Kearney, Keith Rooney, Cathryn Crockett Clinical Oncology, Northern Ireland Cancer Centre, Belfast, United Kingdom Purpose/Objective: Cutaneous squamous cell carcinoma (cSCC) is usually cured with surgery alone, but patients with high-risk factors (HRFs) remain at increased risk of recurrence and disease-specific mortality (DSM) (1-3). Adjuvant radiotherapy (ART) is commonly utilised in this context, however without any grade I evidence we are unclear if this leads to better outcomes. This review examines the impact of HRFs on outcomes in patients treated with ART within our centre. Material/Methods: A retrospective single centre analysis was conducted to identify patients with node negative cSCC treated with ART from 2017-2022 in the Northern Ireland Cancer Centre (NICC). HRFs including surgical margin <1mm, recurrence, diameter >20mm, aggressive histology, perineural invasion, thickness >6mm or
Table 2. Outcomes post ART
Conclusion: HRFs are major predictors of outcome in cSCC, even
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