Frequency and outcomes of midline gliomas in a tertiary care hospital in Pakistan: a retrospective study

Introduction: Midline structures in the central nervous system include the thalamus, brainstem, and spinal cord. Within the midline tumors, Diffuse midline gliomas (DMGs) and diffuse intrinsic pontine gliomas (DIPG) have a poor prognosis. DMGs are inclusive of all diffuse intrinsic pontine gliomas (DIPG), previously usually used for only pontine gliomas, to emphasize that these lesions are not solely centered in the pons/brainstem. In this retrospective review, we aim to report the frequency and outcomes of midline gliomas amongst all midline tumors in a tertiary care setup. Methods: Data were collected retrospectively from the medical records at Aga Khan University Hospital between 2013 and 2023. All patients aged 18 and younger with tumors in midline locations were reviewed, and 102 patients were included. A few tumor samples were also sent to SickKids, Toronto, for molecular testing. Results: Our cohort represents 102 patients with midline tumors, a median age of 11 years (interquartile range (IQR): 7.75–15 years), and a similar male-to-female ratio. Most patients presented with limb weakness and headache (median duration: 1.5 months, IQR: 1–4 months). The most common site of tumors was the brainstem, followed by the spine and thalamus. Sixty-six patients had surgery: 2 DIPGs, 15 low-grade gliomas, 13 ependymomas, 8 high-grade gliomas, 12 diffuse midline glioma, and 16 other tumors were identified. All of the patients diagnosed with DMG had H3K27 alteration on immunohistochemistry. Thirty-six patients were diagnosed via radiology: 33 DIPG and 3 tectal plate glioma. Only 10 patients received chemotherapy, and radiation therapy was given to 24 patients. Overall survival for all midline tumors was 53.9%, with 47 events. Conclusion: Our study depicts poor survival outcomes at one year of patients diagnosed with DMG (16.7%) and DIPG (14.3%) amongst all midline tumors, regardless of radiation therapy or concurrent chemoradiotherapy. To improve the care and survival of all midline tumors, there is a dire need for affordable diagnostic techniques in specialized centers across low- and middle-income countries.