ESTRO 2025 - Abstract Book

S1703

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

Figure 1. Response to RTH+HT. On tle left - 3.5cm oligoprogressive metastasis to axillary lymph nodes prior to treatment (10/2020). On the right - patient exhibited complete response (CR) in irradiated lesion following treatment (04/2022). Additionally, patient achieved a systemic CR. Conclusion: Both RTH+HT and RTH alone provide long-lasting local responses in nearly half of the patients. Early post radiotherapy evaluation (1-2 months) may not correlate with final local response to treatment. Optimal radiological evaluation occurs 3-4 months after treatment.

Keywords: melanoma, oligoprogression, hyperthermia

2932

Digital Poster BCC where the sun doesn't shine.

Peter Mbanu, Victoria Lavin, Nooreen Alam, Imogen Hemy, Lucy Buckley, Sarah Mitchell Clinical Oncology, The Christie NHS Foundation Trust, Manchester, United Kingdom

Purpose/Objective: Peri-anal cancers are rare cancers which account for less than 1% of solid tumours. Peri-anal basal cell cancers (BCC) only account for less than 1% of all anal cancers, making peri-anal basal cell cancer very rare.[1] The predominant cancer at this location is squamous cell cancer. Basal cell cancers mainly occur in skin areas exposed to the sun. They seldom metastasise or cause local symptoms and are generally slow-growing lesions. Patients usually have a mean age above 70.[2] Peri-anal BCC is primarily treated with complete surgical resection. Surgical resection in this part of the body comes with the usual common surgical risks and potentially life-changing risks for patients, such as fistula and incontinence. It also involves two surgical specialities, colorectal and plastic surgeons. Given the low risk of metastasis and high risk of surgery, can surgery be reserved only for patients with radiotherapy-resistant or recurrent disease? Material/Methods: Four patients were referred to our centre with perianal BCC over the last four years (2020 to 2024). All patients had histological confirmation of basal cell cancer. There were three males and one female, aged between 72 and 91. They all were staged both clinically and radiologically with MR and PETCT. Radical radiotherapy treatment was delivered to all patients, with patients receiving 45Gy in 20 fractions. The V-MAT plan covered the area of disease marked out as GTV, with 1cm to CTV and another 1cm to PTV. They all completed their treatment with minimal radiotherapy toxicity, which was mainly RTOG G1 and 2a skin toxicity. Patients were followed up on the standard anal radiotherapy follow-up pathway with clinical review and examination at 6 weeks, then three monthly for the