The prognostic impact of MGMT expression on low-grade gangliogliomas: a clinicopathological and immunohistochemical study

Ganglioglioma (GG) is an uncommon brain parenchymal neoplasm. Although most cases have indolent clinical behaviour, a subgroup of GGs does recur, especially in patients with unresectable disease. O6-methylguanine DNA methyltransferase (MGMT) is a DNA repair protein that removes mutagenic and cytotoxic adducts from O6-guanine in DNA. Lack of MGMT protein expression immunohistochemically is related to drug responses in patients with malignant glioma treated with alkylating agents. Furthermore, MGMT promoter methylation has also been investigated as an independent favourable prognostic factor for glioblastoma. The primary management is surgical resection for GGs and gross total resection is recommended. Despite infrequent use of chemotherapy for low-grade GGs, it was still introduced to a subset of patients, especially those who had unresectable disease. We assessed clinicopathological features of nine cases of low-grade GG to further elucidate the relationship between the status of the MGMT protein expression and the prognosis. This series included four men and five women with a mean age of 21.6 years at the first surgery. The mean postoperative follow-up period was 6 years. Only two patients had recurrent disease after 1.7 and 3.2 years of the first surgery. Immunohistochemically, 11.1% exhibited 3+ nuclear staining for MGMT protein, 11.1% exhibited 2+ staining, 33.3% exhibited 1+ staining, and 44.4% exhibited 0 staining. Tumours with more intensive MGMT protein expression (2+~3+ immunostaining) tended to recur more frequently (p < 0.05), corresponding to the worse prognostic predictive value of intensive MGMT staining.