Midline Gliomas: A Retrospective Study from a Cancer Center in the Middle East

SIMPLE SUMMARY: Midline gliomas are tumors that can manifest as either circumscribed or diffuse growths. These tumors typically develop in midline structures, including the thalamus, brainstem, and spinal cord. Other structures along the midline, such as the corpus callosum, basal ganglia, ventricles, paraventricular structures, and cerebellum may also be affected. Diffuse midline gliomas (DMGs) are a subtype of midline gliomas and are considered highly aggressive and are most commonly diagnosed in children and young adults. These tumors are difficult to treat due to their location and invasive nature, and their prognosis is generally poor. We aim to describe our experience with midline gliomas, with a focus on DMGs. ABSTRACT: Midline gliomas are tumors that occur in midline structures and can be circumscribed or diffuse. Classical midline structures include the thalamus, brainstem, and spinal cord. Other midline structures include the corpus callosum, basal ganglia, ventricles, paraventricular structures, and cerebellum. Diffuse midline glioma (DMG) is a diffuse glioma that occurs in the classical midline structures, characterized by a specific genetic alteration, and associated with grim outcome. This study was conducted at King Hussein Cancer Center and reviewed the medical records of 104 patients with circumscribed and diffuse gliomas involving midline structures that underwent biopsy between 2005 and 2022. We included a final cohort of 104 patients characterized by a median age of 23 years and a male-to-female ratio of 1.59-to-1. Diffuse high-grade glioma (DHGG) was the most common pathological variant (41.4%), followed by DMG (28.9%). GFAP was positive in most cases (71.2%). Common positive mutations/alterations detected by surrogate immunostains included H3 K27me3 (28.9%), p53 (25.0%), and H3 K27M (20.2%). Age group, type of treatment, and immunohistochemistry were significantly associated with both the location of the tumor and tumor variant (all; p < 0.05). DMGs were predominantly found in the thalamus, whereas circumscribed gliomas were most commonly observed in the spinal cord. None of the diffuse gliomas outside the classical location, or circumscribed gliomas harbored the defining DMG mutations. The median overall survival (OS) for the entire cohort was 10.6 months. Only the tumor variant (i.e., circumscribed gliomas) and radiotherapy were independent prognosticators on multivariate analysis.