Stereotactic radiotherapy for oligometastatic mediastinal lymph-nodes: a multicentre retrospective experience

Mediastinal oligometastases represent a clinical and technical challenge, due to the need to combine optimal treatment with the risk of severe toxicity. In this retrospective multicentre experience, we report the data of a cohort of patients treated with stereotactic body radiotherapy (SBRT) for oligometastatic mediastinal lymph-nodes. Inclusion criteria of the study were: written informed consent for the treatment, ECOG PS ≤ 2, diagnosis of oligometastatic mediastinal lymph-nodes up to 5 lesions being the mediastinum the only active site of disease, patients treated with radiotherapy schedules applying a minimum 6 Gy per fraction. Prior radiotherapy to the mediastinum was not considered as an exclusion criterion. A total of 63 lymph-node metastases in 49 patients with median age of 69.5 years (range 47-83 years) received SBRT between September 2020 and April 2024, for a median total dose of 30 Gy (range 21-50 Gy) in 5 fractions (range 3-5). With a median follow-up of 15 months, 1- and 2-year local control rates were 96.9% and 91.8%, while distant progression-free survival rates were 66.7% and 30.2%. Median time to new systemic therapy was 12 months, while 1- and 2-year polymetastatic-free survival (PMFS) and overall survival (OS) were respectively 78% and 64%, and 86.2% and 75.8%. At statistical analysis, patients who develop a further oligoprogression treated with a second course of SBRT have a longer time to new systemic treatment (p = 0.017), being genitourinary and gynecological malignancies related to improved PMFS and OS at univariate analysis. Only one late G3 adverse event was observed, consisting of dysphagia treated with intravenous steroids. In our series, SBRT for oligometastatic mediastinal lymph-nodes was safe with a single G3 late adverse event, with promising results in terms of local control and time to activation of a new systemic therapy.