What is medulloblastoma, the most common brain tumor in children?

Among children under 15 years of age, tumors of the central nervous system are the most common cancer (27%), followed by leukemia (28%). Among these tumors of the central nervous system, brain tumors affect about 500 children each year. These are fetal tumors, gliomas, ependymomas, etc. These pediatric tumors are biologically very different from those of adults and develop in highly sensitive regions, which are still developing.

Embryonic tumor family

Medulloblastoma is the most common malignant brain tumor in children with an incidence of 1 in every 20,000 children and a peak incidence between the ages of 2 and 8 years. They are part of the family of embryonal tumors (which develop from primitive cells, called embryos) and usually originate in the cerebellum, an area located under the cerebral hemispheres and behind the brain stem.

Medulloblastoma forms a very heterogeneous group of tumors, which are divided into four subgroups. These were identified based on prognostic and expressed genes. Treatment – survival rates do not exceed 70% to 80% at 5 years. For some subtypes, the prognosis is worse. Ultimately, the average survival rate for medulloblastoma is lower than the 5-year survival average for all pediatric cancers, at about 83%.

Often an aggressive tumor

This, in particular, is due to its aggressiveness. tumor “is aggressive and can metastasize throughout the central nervous system through the cerebrospinal fluid. At the time of diagnosis, about half of children have metastases that are rarely symptomatic”, Notes on its website Gustave-Roussy Anticancer Center (Villejuif).

Intracranial hypertension is the first sign of medulloblastoma. she “A more or less marked balance disorder is associated. Cranial nerve palsy may occur if the brainstem is infiltrated by the tumor. The motor pathways are usually affected posteriorly”, Gustave-Roussy adds center. Diagnosis is based on MRI and biopsy.

Treatment includes surgery, chemotherapy and radiotherapy. While surgery is often the first step, chemotherapy is sometimes given before removing the tumor, especially if it is metastatic. In children under 5 years of age, radiotherapy, which is particularly toxic, is avoided as much as possible.

The success of the treatment depends on the quality of the surgery (complete or not), the presence or absence of metastases and the biological factors of the tumor. We talk about standard risk – when all conditions are met for treatment to be successful. In high-risk patients, survival rates drop to 30 to 60%.

Lack of targeted treatment

Despite the identification of subgroups, targeted treatments for these brain tumors are not sufficiently developed. This is why at the Curie Institute (Paris) Dr. A “Signaling, Development and Brain Tumors” team was created under the leadership of Olivier Ayrault. Thus, in 2018, the signaling team was able to identify the involvement of the SRC protein in group 4 medulloblastoma, which is the most common. “Studies are ongoing to evaluate how to target this SRC protein and develop new therapeutic strategies. This work is being carried out internationally (Germany, England, Canada, Japan and the United States) and in direct collaboration with clinical teams. France, especially in the framework of Paris Kids Cancer supported by AP-HP, Gustave Roussy and Institut Curie”, A press release mentions the Curie Institute.

Another team at the institute is working more precisely on a subtype called “Group 3,” which is particularly aggressive. Again, no targeted treatment is available. After discovering the signaling pathway activated in this cancer, researchers identified a drug that targets this signaling pathway.

Thus, the development of targeted and more effective treatments first requires a better understanding of all the mechanisms involved in the generation of medulloblastoma cancer cells.