A glioma is a tumor that originates from the supportive glial cells of the brain or spinal cord. These tumors represent about 30% of all brain and central nervous system tumors and 80% of all malignant brain tumors. For patients and their families, this diagnosis begins a complex medical journey defined by the tumor’s location within the body’s most intricate organ.
The Nature of Infiltration in Gliomas
A defining characteristic of most gliomas is their infiltrative, or diffuse, nature. Individual tumor cells grow into and intermingle with surrounding healthy brain tissue, much like the roots of a tree spreading through soil. This creates a tumor without clear borders, as microscopic tendrils can extend far beyond the main mass visible on imaging scans.
This contrasts with non-infiltrating, or circumscribed, tumors, which grow as a solid mass that pushes brain tissue aside rather than invading it. Circumscribed tumors, like pilocytic astrocytomas (WHO Grade 1), have well-defined margins that allow for more complete surgical removal. Because their cells are interwoven with functional brain tissue, infiltrating gliomas are nearly impossible to remove entirely with surgery, which is a primary reason for tumor recurrence.
The World Health Organization (WHO) classifies gliomas into grades 1 through 4 based on their microscopic appearance and molecular features, indicating how aggressively they behave. Diffuse gliomas include WHO Grade 2 (low-grade) and Grades 3 and 4 (high-grade) tumors. Common types of adult diffuse gliomas are astrocytomas and oligodendrogliomas. Glioblastoma, designated as WHO Grade 4, is the most common and aggressive type of infiltrating glioma.
Modern classification has become more refined by incorporating molecular markers. Adult diffuse gliomas are now primarily categorized based on the status of the isocitrate dehydrogenase (IDH) gene. The main types are IDH-mutant astrocytoma, IDH-mutant and 1p/19q-codeleted oligodendroglioma, and IDH-wildtype glioblastoma. These molecular distinctions are important as they correlate with the tumor’s natural course.
Recognizing Signs and the Diagnostic Process
The discovery of a glioma often begins with non-specific symptoms that depend on the tumor’s size and location. Persistent or worsening headaches, often more intense in the morning, are a common sign caused by increased pressure within the skull. Other indicators can include new-onset seizures as the tumor disrupts the brain’s normal electrical activity.
Cognitive or personality changes, such as memory problems or shifts in mood, can also signal a tumor’s presence. Depending on the affected brain region, individuals might experience weakness on one side of the body, speech difficulties, or vision problems. A thorough medical evaluation is necessary to determine the cause of these symptoms.
The diagnostic process starts with a consultation and a detailed neurological exam, where a doctor assesses functions like vision, hearing, balance, and coordination. If a brain tumor is suspected, the primary tool for visualization is magnetic resonance imaging (MRI). An MRI provides detailed pictures of the brain, revealing the tumor’s location and size.
While imaging provides strong evidence, a biopsy is the definitive step for diagnosis. This procedure involves surgically removing a small sample of tumor tissue for examination by a pathologist. The biopsy confirms the growth is a glioma, determines its grade, and allows for analysis of specific molecular markers like IDH mutations. This information is used to guide treatment decisions.
Current Therapeutic Strategies
The treatment for infiltrating gliomas is a multimodal approach combining several strategies. Surgery is often the first step, with the goal of “maximal safe resection,” which means removing as much of the tumor as can be safely accomplished without damaging important brain functions.
Following surgery, radiation therapy is used to target and destroy residual cancer cells. This treatment uses high-energy beams, like X-rays, aimed at the tumor site over several weeks. Radiation is often administered with chemotherapy to enhance its effectiveness, and this combined approach is the standard of care for high-grade gliomas.
Chemotherapy uses drugs to kill cancer cells, with the oral agent temozolomide being the most common for gliomas. It is often given during and after radiation therapy. Newer approaches include targeted therapies, which use drugs designed to attack specific molecular characteristics in tumor cells. Tumor Treating Fields (TTFields) therapy, which uses an electrical field to disrupt cell division, is another option for aggressive gliomas like glioblastoma.
Managing Disease Progression and Outlook
The long-term outlook for an individual with an infiltrating glioma is highly variable. Prognosis depends on the tumor’s grade, with lower-grade gliomas having a more favorable outlook than high-grade ones. The tumor’s molecular profile, such as an IDH mutation, is also a primary factor in predicting its behavior and response to therapy. Other contributors include the patient’s age, overall health, and the extent of surgical tumor removal.
Even after successful initial treatment, it is expected that the glioma will eventually grow back. This reality necessitates a plan for long-term management and vigilant monitoring. Regular surveillance with MRI scans is standard practice to detect any signs of tumor progression or recurrence as early as possible.
Managing a glioma is a continuous process focused on controlling the tumor and maintaining the best possible quality of life. This requires a multidisciplinary care team that may include neuro-oncologists, neurosurgeons, radiation oncologists, and palliative care specialists. Palliative care can be introduced early to help manage symptoms and provide an extra layer of support for the patient and their family.