ESTRO 2025 - Abstract Book

S1063

Clinical – Head & neck

ESTRO 2025

objective was to analyse oncological outcomes in patients with PDS referred for adjuvant radiotherapy in order to better inform our future practice.

Material/Methods: Ethics board approval was sought. Retrospective analysis from 2010 – 2024 of our institutional pathological database detailing all histologically diagnosed cases of PDS. These cases were then crosschecked against our radiotherapy facility’s database in order to examine those post-operative patients who had been referred for adjuvant radiotherapy. Only patients in whom the final histological diagnosis confirmed PDS were included. Patient details, clinicopathological information and radiotherapy dose fractionation and target volume details were recorded. Margins were reported as negative when ≥ 1mm and close where <1mm. Results: 22 cases were reviewed, with six patients excluded in whom the final histological report could not definitively distinguish between PDS and alternative diagnoses following specialist dermatopathologist review at a dedicated MDT. 16 patients with histologically confirmed PDS were included. All patients were male, with a median age of 75 (Range 63-93). 10 (69%) were located n the scalp, three on the temple, two on the pinna and one on the cheek. 6 (38%) of these patients were immunosuppressed. 2 patients were referred for adjuvant radiotherapy in the setting of recurrent disease. 8 patients had clear margins, 6 had close margins and 2 patients had microscopically positive margins. 2 specimens each were reported as containing perineural or vascular invasion; no specimens contained both. 13 (81%) completed adjuvant radiotherapy. Seven patients completed 60Gy/30 IMRT, four 50Gy/20 and two underwent 50Gy/20 orthovoltage RT. Of those that completed RT, no locoregional recurrences were recorded and 11/13 (85%) remain disease-free at a median follow up of 49 months (Range 6 – 84). 19% of patients died, two due to metastatic PDS and one due to an unrelated malignancy.

Conclusion: Adjuvant radiotherapy is an effective measure in offering local control in high risk cases of PDS.

Keywords: Pleomorphic dermal sarcoma

References: 1. Bowe CM, Godhania B, Whittaker M, Walsh S.Pleomorphic dermal sarcoma: a clinical and histological review of 49 cases. Br J Oral Maxillofac Surg. 2021. May;59(4):460-465. doi: 10.1016/j.bjoms.2020.09.007. Epub 2020 Sep 11. 2. Fruergaard O, Ørholt M, Vester-Glowinski PV, Jensen DH. The incidence of atypical fibroxanthoma and pleomorphic dermal sarcoma in Denmark from 2002 to 2022. Surg Oncol. 2024 Sep 26:57:102147. doi: 10.1016/j.suronc.2024.102147. 3. Miller K, Goodlad JR, Brenn T. Pleomorphic dermal sarcoma: adverse histologic features predict aggressive behavior and allow distinction from atypical fibroxanthoma. Am J Surg Pathol. 2012;36(9):1317-1326

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Digital Poster Stereotactic boost radiotherapy to head and neck cancer patients: single institution experience Vitali Moiseenko, Asim Biloo, Brian Zegers, Loren Mell, Parag Sanghvi Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, USA Purpose/Objective: Head and neck cancer patients receiving conventionally fractionated radiotherapy treated with a definitive intent are typically prescribed 70-72 Gy to gross disease. In sino-nasal cancer patients with T4 disease with intra-cranial involvement, this can be a challenge to deliver upfront when tumors abut optic structures or brain. It is our policy to start these patients with an upfront plan of 46-54 Gy treating both the primary tumor and elective lymph nodes. We