The role of PD-L1 in biological behavior of intracranial meningiomas

Meningiomas are considered a substantially benign disease that can be treated surgically in the vast majority of patients. However, there are forms of meningioma characterized by greater aggressiveness and/or tendency to recurrence. To date, grading is the only known factor that provides some information about the biological behavior of meningiomas. As a matter of fact, patients with high grade meningiomas (WHO grade 2 and 3) have a significant higher risk to develop local recurrence after treatment and, consequently, they tend to have a shorter survival compared to patients with WHO grade 1 meningiomas .However, even grade 1 meningiomas can recur even if with less frequency. Given that to date there are no approved pharmacological treatments for meningiomas and that the use of treatments such as hormone-therapy and chemotherapy have not shown any substantial benefit, it seems appropriate to hypothesize new innovative therapeutic strategies and verify their biological plausibility. To our knowledge, this is the first report of increased PD-L1 expression in meningioma recurrences compared to their primary presentation, regardless of their grade. The high prevalence of PD-L1 expression in the meningioma population and its correlation with grade and clinical behavior may be an important tool to tailor therapeutical strategies and follow up, in particular in high grade and recurrent cases. Moreover, the results obtained contribute to build a rational basis for designing therapeutic trials that use immunotherapy in the treatment of meningiomas.