Glioblastoma is the most aggressive and common type of cancer. This malignant tumor starts in glial cells, specifically astrocytes, which support nerve cells. Despite medical advancements, glioblastoma carries a challenging prognosis, with median survival generally ranging from 12 to 18 months and a five-year survival rate of less than 10%.
Glioblastoma and Genetic Inheritance
Glioblastoma is rarely considered hereditary or directly passed down through families. The vast majority of glioblastoma cases, over 90%, are sporadic, meaning they occur randomly without an inherited genetic link. Having a family member with glioblastoma does not significantly increase an individual’s own risk in most situations. Approximately 5% of cases are linked to certain hereditary syndromes, but these are exceptions rather than the norm.
Identified Risk Factors for Glioblastoma
Since glioblastoma is seldom inherited, other factors contribute to its development. Age is a significant risk factor, as glioblastomas are most commonly diagnosed in older adults, with the average age being around 64 years. The incidence increases with age, peaking between 75 and 84 years.
Previous exposure to ionizing radiation, such as childhood cancer radiation therapy, is another recognized risk factor. Prolonged exposure to certain chemicals, including pesticides, petroleum products, synthetic rubber, and vinyl chloride, may elevate the risk. Men show a slightly higher risk than women.
Understanding Genetic Predisposition Syndromes
In rare instances, glioblastoma can be part of an inherited genetic predisposition syndrome that increases the risk of various cancers.
Neurofibromatosis Type 1 (NF1)
Neurofibromatosis Type 1 (NF1) is one such syndrome, caused by mutations in the NF1 gene, which increases susceptibility to several tumors, including glioblastoma. Individuals with NF1-mutated glioblastoma may have a lower overall survival rate.
Li-Fraumeni Syndrome
Li-Fraumeni Syndrome is another rare condition, linked to TP53 tumor suppressor gene mutations. This syndrome raises the risk for a wide spectrum of cancers, including brain tumors like glioblastoma. Gliomas arising in individuals with Li-Fraumeni syndrome often present at a younger age than sporadic cases.
Lynch Syndrome
Lynch Syndrome, also known as HNPCC, results from mutations in DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6, PMS2). Predominantly associated with colorectal and endometrial cancers, Lynch Syndrome also increases the risk of brain tumors, including glioblastoma.
Turcot Syndrome
Turcot Syndrome is a distinct, rare condition characterized by the presence of both colorectal polyps and brain tumors, including glioblastoma or medulloblastoma. This syndrome is linked to mutations in either the APC gene or the MMR genes, depending on the type.
Genetic Counseling and Evaluation
Genetic counseling provides a valuable resource for individuals concerned about a family history of glioblastoma or other cancers. It is recommended for a strong family history of rare cancers, cancers diagnosed at an unusually early age, or if a specific cancer-causing genetic mutation is known within the family. Counseling involves a comprehensive risk assessment based on personal and family medical history. A genetic counselor discusses the potential benefits and limitations of genetic testing options. They explain the implications of test results for the individual and their family, guiding informed decisions about further evaluation or management.