Evaluating the Impact of Minimal Dose on Survival Outcomes in Melanoma Patients Treated with Gamma Knife Radiosurgery

Introduction: Brain metastases from melanoma present unique challenges due to the radioresistant nature of melanoma cells, which possess mechanisms such as enhanced DNA repair pathways and resistance to radiation-induced apoptosis. Gamma Knife (GK) stereotactic radiosurgery (SRS) has become a crucial modality in managing brain metastases, allowing for high-dose, precise targeting of tumor tissue. However, the role of minimal radiation dose on clinical outcomes, particularly in terms of overall survival (OS) and progression-free survival (PFS), remains poorly understood.

Methods: We conducted a retrospective analysis of 171 patients with brain metastases from melanoma treated with GK SRS between 2014 and 2024. Patients were categorized into high and low minimal dose groups based on a median dose of 15.5 Gy. Statistical methods, including Spearman correlation, Kaplan-Meier survival analysis, and Cox proportional hazards regression, were used to explore associations between minimal dose and clinical outcomes, adjusting for covariates such as age and Karnofsky Performance Status (KPS).

Results: A significant correlation was found between minimal dose and PFS (r = 0.26, p = 0.0077), indicating a potential role of higher minimal doses in extending PFS. The Cox regression analysis further demonstrated that, while minimal dose was not a significant predictor of OS, it was associated with a lower risk of progression in PFS (HR = 0.9708, 95% CI: [-0.048, -0.011], p = 0.0016).

Conclusion : The findings suggest that minimal dose may play an important role in prolonging PFS in patients with melanoma brain metastases treated with GK. These results underscore the need for optimizing minimal doses to improve tumor control. A minimum dose of 15.5 Gy to the brain metastasis is recommended.