Stereotactic Radiosurgery with or Without Systemic Immune Checkpoint Inhibitors for Melanoma Brain Metastases

Introduction: The impact of ICI coupled with stereotactic radiosurgery SRS was not well understood and was evaluated in the present study.

Methods: Seventy melanoma brain metastasis patients (691 tumors) underwent Gamma Knife SRS between 2017 and 2023. The median age of patients was 66 years (range 30-97 years). Fifty patients (71.43%) received ICI with SRS and 20 patients underwent SRS only. The median KPS was 70 (range 60-100). Thirty-six (51.43%) patients underwent surgical resection for brain metastasis prior to SRS. The median number of metastases per patient was 4 (range 1-28). The median margin dose was 16 Gy (range 8 – 25 Gy) and the median margin isodose was 80% (range 53-95%).

Results: The 1-year OS for patients treated with ICI and SRS was 70% compared to the 46.3% in patients treated with SRS alone (p = 0.178). Patients who underwent ICI treatment (521 tumors) showed significantly better LTC per tumor compared to patients who underwent SRS alone (66 tumors, p = 0.0002). The 1-year and 2-year brain relapse rates were 75.52% and 63.12% respectively, which was not statistically different. (p = 0.61). Six patients (8.57%) had radiographic imaging defined adverse radiation effect (ARE).

Conclusion : The present study demonstrated that adding ICI to SRS improved one year survivals and individual tumor responses, but not late distant intracranial relapse patients with metastatic melanoma brain metastases.