Postoperative LINAC-Based Stereotactic Radiotherapy for Grade I Intracranial Meningioma in Subtype Classification.

Objective: To evaluate outcomes of postoperative radiotherapy (RT) for residual WHO grade I meningioma based on subtype classification and relevant factors that may influence the outcomes.

Material And Method: Medical records from 252 patients, with known histology of intracranial meningioma, who underwent stereotactic RT in Ramathibodi Hospital between 1998 and 2008, were reviewed. One hundred and two out of 252 patients were included. The data were categorized into 2 groups: common subtype (meningothelial and transitional subtypes) and uncommon subtype (fibroblastic, psammomatous, angiomatous, microcystic, secretory, lymphoplasmacyte-rich and metaplastic subtypes). Analysis of tumor control rate, tumor shrinkage rate and risk factors of treatment failure were conducted.

Results: The median of follow-up period was 46 months (interquartile range (IQR): 53). The five-year tumor-control rates of overall, common and uncommon subtypes were 89.9%, 92.9% and 81.5%, respectively, which showed no significant difference between the two groups, p = 0.108. The five years tumor shrinkage rates of overall, common, and uncommon subtypes were 42.5%, 42.3% and 42.7%, respectively, there was no significant difference, p = 0.934. In univariate analysis, gender (male), total minimal dose and fraction demonstrated statistically significant impact on treatment failure. However, only a total minimal dose had any significant effect in multivariate analysis.

Conclusion: Radiotherapy is highly effective in controlling postoperative residual meningioma. This study may be useful to evaluate patients’ prognosis and possibility of recurrence based on histology subtypes. In addition, total minimal dosage was the sole risk factor of treatment failure found in the present study.