MTAP immunohistochemistry as a surrogate marker of CDKN2A loss in brain tumors: A meta-analysis and literature review.

Given the known relationship between CDKN2A homozygous deletion (HD) and worsened outcomes in both meningiomas and IDH-mutant astrocytomas, it is paramount to identify CDKN2A HD for accurate risk stratification of patients. Multiple array platforms can detect CDKN2A HD. However, these methods are expensive and are not readily available at every institution. To address this, we conducted a meta-analysis and literature review to evaluate 5'-methylthioadenosine phosphorylase (MTAP) expression determined by immunohistochemistry (IHC) as a surrogate of CDKN2A HD. Our study analyzed 7 cohort studies, 3 of which focused on meningiomas encompassing a total of 87 patients; and 4 studies were conducted on infiltrating glioma patients, consisting of 423 patients. Our results show that despite utilizing different MTAP IHC clones, the results among all studies showed consistently good sensitivity and specificity. The overall sensitivity and specificity of MTAP IHC as a surrogate of CDKN2A HD was excellent with 92.3% and 97.5%, respectively. These results were maintained when MTAP IHC was evaluated in distinct tumor types. MTAP IHC is a good surrogate marker for identifying CDKN2A HD in infiltrating gliomas and meningiomas. MTAP IHC implementation would allow correct integrated diagnosis for institutions that lack DNA sequencing.