Stereotactic body radiation therapy for oligometastatic melanoma: a real-world study of the ESTRO/EORTC nomenclature

The study aims to investigate the efficacy of stereotactic body radiation therapy (SBRT) in melanoma patients with oligometastatic disease (OMD), and to assess the prognostic value of the European Society for Radiotherapy and Oncology (ESTRO) and European Organization for Research and Treatment of Cancer (EORTC) nomenclature for these patients. This is a single-center, retrospective study including all melanoma patients with OMD (n = 66) receiving SBRT between 2010 and 2023. Patients were categorized based on the timing of SBRT of OMD according to the ESTRO/EORTC classification. We analyzed local control, progression-free survival (PFS), overall survival (OS), safety, and prognostic factors. The median follow-up was 72.5 months. Patients were categorized at the timepoint of SBRT as having de novo (n = 20), repeat (n = 25), or induced (n = 21) OMD. The most common OMD subcategories were repeat oligorecurrence (33.3%) and metachronous oligorecurrence (16.7%). Concurrent systemic treatment was administered in 30.3% of the patients. Local control rates at 1, 2, and 3 years was 96.3%, 93.2%, and 93,2%, respectively. The median PFS and OS were 7.7 (95% CI 4.9–12.4) and 26.5 (95% CI 17.6–38.8) months, respectively. No significant differences in PFS or OS were observed between patients with de novo, repeat, or induced OMDs. Similarly, survival outcomes did not differ between patients classified into the oligorecurrence, oligoprogression, or oligopersistence cohorts. However, patients who underwent SBRT targeting all metastatic sites demonstrated significantly improved PFS and OS compared to those with additional non-irradiated lesions (p = 0.022 and p = 0.002, respectively). Moreover, patients with a single metastasis had significantly better PFS and OS than those with 2–5 metastases (p = 0.045 and p = 0.021). However, only ECOG performance status remained significant in the multivariable analysis. Additionally, 19 patients (29%) experienced grade 1–2 SBRT-related side effects. SBRT was well tolerated and demonstrated excellent local control rates in melanoma with OMD. Our findings indicate that there was no significant difference in PFS or OS between the OMDs, suggesting that the prognostic implication of the ESTRO/EORTC classification in melanoma may warrant further evaluation in prospective studies.