Genetic Characteristics of Mismatch Repair-deficient Glioblastoma

A Synopsis of Biomarkers in Glioblastoma: Past and Present

Accounting for 48% of malignant brain tumors in adults, glioblastoma has been of great interest in the last decades, especially in the biomolecular and neurosurgical fields, due to its incurable nature and notable neurological morbidity. The major advancements in neurosurgical technologies have positively influenced the extent of safe tumoral resection, while the latest progress in the biomolecular field of GBM has uncovered new potential therapeutical targets. Although GBM currently has no curative therapy, recent progress has been made in the management of this disease, both from surgical and molecular perspectives. The main current therapeutic approach is multimodal and consists of neurosurgical intervention, radiotherapy, and chemotherapy, mostly with temozolomide. Although most patients will develop treatment resistance and tumor recurrence after surgical removal, biomolecular advancements regarding GBM have contributed to a better understanding of this pathology and its therapeutic management. Over the past few decades, specific biomarkers have been discovered that have helped predict prognosis and treatment responses and contributed to improvements in survival rates.

Lynch Syndrome-Associated Glioblastoma Treated With Concomitant Chemoradiotherapy and Immune Checkpoint Inhibitors: Case Report and Review of Literature

Lynch syndrome (LS) is an autosomal dominant disorder caused by mutations in mismatch repair (MMR) genes and is also known to be associated with glioblastomas. The efficacy of immunotherapy for LS-associated glioblastomas remains unknown. Herein, we report a rare case of LS-associated glioblastoma, treated with chemotherapy using immune checkpoint inhibitors (ICI). A 41-year-old female patient presented with headaches and sensory disturbances in the right upper limb for 6 weeks. She had been treated for rectal cancer and had a family history of LS. MRI revealed two ring-enhancing lesions in the left precentral gyrus. She underwent subtotal resection, leading to a pathological diagnosis of isocitrate dehydrogenase wild-type glioblastoma. She received daily administration of (temozolomide, 75 mg/m²) and concurrent radiotherapy (60 Gy) postoperatively. However, the tumor recurred 1 year after the initial treatment. A molecular genetic study showed high microsatellite instability (MSI), and she was treated with pembrolizumab therapy. Disease progression occurred despite six cycles of pembrolizumab therapy and radiotherapy at the dose of 40 Gy. She died due to glioblastoma progression 19 months after the initial treatment. The present case demonstrates that some LS-associated glioblastomas may be resistant to ICI despite high MSI, possibly because of intratumor heterogeneity related to MMR deficiency.