Biological effective dose as a predictor of local tumor control in stereotactic radiosurgery treated parasellar meningioma patients

Abstract

Purpose: The radio-surgical literature increasingly uses biological effective dose (BED) to replace absorbed dose to analyze outcome of stereotactic radiosurgery (SRS). There are as yet no studies which specifically investigate the association of BED to local tumor control in para-sellar meningioma. Methods: Retrospective analysis of patients underwent stereotactic radiosurgery (SRS) for para-sellar meningioma during the period of 1995-2022. Demographic, clinical, SRS parameters, and outcome data were collected. The target margin BED with and without a model for sub-lethal repair was calculated, as well as a ratio of BED at the target margin to the absorbed dose at the target margin. Factors of local control were further analyzed Results: The study was comprised of 91 patients. The median age was 55. 34 (37%) patients had a resection of their meningioma prior to SRS. The median clinical follow up was 89 months. 13 (14.3%) patients were found to have progression. 3-, 5- and 10-years local tumor control were 98%, 92% and 77%, respectively. In cox univariate analysis, the following factors were significant: Number of prior surgical resections (Hazard Ratio [HR] = 1.82, 95% CI = 1.08-3.05, p = 0.024), BED (HR = 0.96, 95% CI = 0.92-1.00, p=0.03), and BED/margin (HR = 0.44, 95% CI = 0.21-0.92, p=0.028). A BED threshold above 68 Gy was associated significantly with tumor control (P=0.04). Conclusion: BED and BED /margin absorbed dose ratio can be predictors of local control after SRS in parasellar meningioma. Optimizing the BED above 68Gy_2.47 may afford better long-term tumor control.