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

Introduction: The radio-surgical literature increasingly uses biological effective dose (BED) as a replacement for 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: we did a 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 related to local control were further analyzed.

Results: The study was comprised of 91 patients, 20 (22.0%) and 71 (78.0%) of whom were male and female, respectively. The median age was 55.0 (interquartile range Q1, Q3:47.5,65.5years). 34 (37%) patients had a resection of their meningioma prior to SRS. The median interval from SRS to last clinical follow up or progression 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.