ESTRO 2025 - Abstract Book

S1707

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

lack of evidence, we conducted a single-institution study to test the hypothesis that RTH would prolong time on systemic treatment in metastatic melanoma (MM).

Material/Methods: Patients with MM who received RTH or RTH+HT for oligoprogressive lesions at the referral center between 2018 and 2023 were identified. Oligoprogression was defined as up to five progressive metastases. Systemic treatment included immunotherapy and BRAF/MEK inhibitors. All patients who received radiotherapy to the brain were excluded. The primary endpoint was time to the next systemic therapy (TTNST) after RTH/RTH+HT. The secondary endpoints included overall survival (OS) and progression-free survival (PFS). Factors influencing TTNST, such as median biologically effective dose (BED), total RTH dose, and systemic treatment regimen, were analyzed. Results: The 156 patients were included, 82 pts had RTH+HT while 74 had RTH only, and 184 lesions were irradiated. The median follow-up was 23 months (15.2-34 m). Immunotherapy was used in 82.7% and BRAF/MEK inhibitors in 17.3% of patients. The median total dose of RTH was 32 Gy (10-50 Gy), and the median biologically effective dose (BED) was 108.8 Gy. The median TTNST was 28 months for patients who received RTH and 14 months for patients who received RTH+HT (p=0.6). The median PFS from local treatment was 8 months for patients who received RTH and 10 months for patients who received RTH+HT (p=0.9). The median OS from diagnosis was 147 months for patients who received RTH and was not reached for patients who received RTH+HT (p=0.2). The median OS from radiotherapy was 50 for patients who received RTH and was not reached for patients who received RTH+HT (p=0.031) (Figure 1). None of the analyzed factors influenced median TTNST.

Figure 1

Conclusion: The combination of RTH and HT may prove more efficacious than RTH alone in the systemic treatment of patients, especially for OS. Both RTH and RTH+HT have been demonstrated to extend the duration of systemic treatment in patients.