Glioma accounts for 40-50% of all intracranial tumors and is the most common intracranial tumor. For a long time some people have been treating glioma as the same as cancer in the brain, but this is not actually the case. First of all, a huge difference is that gliomas do not usually metastasize or spread like other malignant tumors. Secondly, glioma has different pathological grade or malignancy. The pathological grade and malignancy are important for the treatment and prognosis of the tumor, the most malignant glioma can have a recurrence period shorter than half a year, and some low grade glioma can have a survival period of more than 10 years or even be cured, which is not available in other systemic tumors.
Pathological grade and malignancy of glioma
The pathological grade of glioma is made by pathologists under the microscope according to the tissue structure and cellular characteristics of the tumor, which is generally divided into 3~4 grades, in order of glioma grade 1, 2, 3 and 4.
Grade 1 is generally benign with hairy cell type astrocytes, accounting for about 5% of gliomas, and is curable;
Grade 2 is a general astrocytoma or astro-oligodendroglioma, accounting for about 30-40% of gliomas, with a prognosis of 5-10 years or even longer.
Grade 3 is mesenchymal astrocytoma, which accounts for about 15-25% of gliomas and generally evolves from grade 2, with an average survival of about 2-3 years.
Grade 4 is glioblastoma, accounting for about 1/3 of gliomas, and the average survival time is usually about six months to two years.
However, it is common for glioma heterogeneity to cause differences in sampling and subjective judgment errors among pathologists resulting in high or low pathologic grade.
Imaging assessment of pathological grade or malignancy of glioma
In today’s highly advanced imaging technology, more than 90% of glioma pathology or malignancy can be correctly determined preoperatively by experienced neurosurgeons, which seems to be more significant for the development of surgical or treatment plans than postoperative pathological diagnosis.
The MRI features of different grades of gliomas are briefly described as follows.
Grade 1 gliomas may have no or uniform enhancement with clear borders generally without edema.
Grade 2 gliomas generally have no enhancement and poorly defined borders.
Grade 3 gliomas may have local enhancement, but no enhancement with moderate edema.
Grade 4 gliomas generally have significant enhancement and edema, and may have necrotic areas.
Surgical treatment of glioma
The current treatment principle of glioma is mainly surgery, and then supplemented with different radiotherapy and drug therapy, i.e. chemotherapy, according to the surgical resection.
How to treat a glioma or which method to choose for treatment should mainly refer to the grade of the glioma and the location of the tumor in the brain, and of course, the patient’s age and physical condition and other factors. A successful surgical treatment should maximize the removal of the tumor and ensure the patient’s life safety and postoperative function, which actually requires the surgeon to have a good ability to identify the tumor tissue, normal neural tissue and the anatomical region where the tumor is located. Because glioma occurs from the brain tissue itself, it is not easy to identify tumor tissue from normal neural tissue and edema tissue. Over-conservatism will cause a large amount of tumor residue to recur soon after surgery, and on the contrary, it will lead to serious functional impairment (hemiparesis, aphasia, etc.) of the patient after surgery.
Grade 1 glioma is not infiltrated, so every effort should be made to achieve total excision, because total excision can be cured, otherwise it will recur.
Treatment of grade 2 glioma is more complicated because not all grade 2 tumors are operated on immediately upon diagnosis. Grade 2 gliomas are often a mixture of tumor cells and normal nerve cells and grow slowly.
If the tumor is located in an important functional area, the normal nerve cells may be removed at the same time, resulting in postoperative dysfunction.
I have had some patients with low grade gliomas in functional areas who were diagnosed and then operated on after 3-5 years of follow-up to obtain the same therapeutic results, but the important thing is that they have gained 3-5 years of near normal life and work time.
Grade 3 gliomas should be removed as much as possible while preserving function, especially the areas showing enhancement, as these areas are the most malignant parts of the tumor remaining will recur quickly.
Grade 4 glioma should be resected as thoroughly and extensively as possible, including some non-functional edema zones, because of the rapid growth of tumor and serious infiltration into the surrounding area.
Radiotherapy and chemotherapy of glioma
Radiotherapy includes general radiotherapy, stereotactic radiotherapy (r-knife and X-knife, etc.) and internal radiation, and general radiotherapy is more commonly used because of the infiltrative growth of glioma.
Chemotherapy, i.e., drug therapy, includes temozolomide and methotrexate, etc. It is mainly used as adjuvant treatment after surgery for gliomas of grade 3 or above.