What is Medulloblastoma?
A medulloblastoma is a tumor that affects the cerebellum, a part of the brain near the base of the skull involved in movement, coordination, and balance. Medulloblastomas are primary central nervous system (CNS) tumors, meaning that they begin in the CNS and do not migrate from somewhere else in the body. However, about a third of the time, medulloblastomas spread to other parts of the CNS via the cerebrospinal fluid (CSF).
Medulloblastomas originate in neuroepithelial cells – stem cells vital in nervous-system development during a baby’s embryonic stage.
Types of Medulloblastoma
Medulloblastomas are always classified as Grade IV tumors, meaning that they are cancerous, fast-growing, and potentially invasive. Beyond that classification, the tumors are grouped into four different subtypes according to their molecular characteristics:
- Group 3
- Group 4
A tumor’s subtype will guide doctors in determining the most appropriate course of treatment.
Symptoms of Medulloblastoma
Common symptoms of medulloblastomas include:
- Problems with balance or coordination
- Difficulty walking
- Nausea or vomiting
- Vision problems
- Uncontrollable eye movements
- Lethargy or fatigue
- Accumulation of fluid in the brain (hydrocephalus)
What Causes Medulloblastoma?
The root cause of a brain tumor is a mutation or damage in the genes that control the growth of affected cells. The specific cause of the gene damage that triggers a tumor’s formation is usually not identifiable. In a healthy cell, these genes prevent the cell from growing or reproducing too rapidly, and the genes can also determine the cell’s normal lifespan. In a tumor’s cells, the damage to the genes causes the cells to grow and reproduce rapidly, and the cells may live longer than usual. As this rapid growth and reproduction continue, the cells grow into an abnormal mass.
Is Medulloblastoma Hereditary?
Most medulloblastomas do not appear to be linked to inherited traits. Instead, researchers believe most gene changes that cause tumors come from external environmental factors or changes within cells that occur randomly and with no external trigger. However, some types of medulloblastoma have been associated with inherited disorders such as Turcot syndrome or Gorlin syndrome.
How Is Medulloblastoma Detected?
Medulloblastomas originate in the cerebellum, a part of the brain responsible for coordination and movement. Because of this, early signs may include coordination and movement-related difficulties. The tumors also often cause fluid build-up in the brain (hydrocephalus), leading to symptoms such as headaches or nausea. Tumors that have spread to the spinal column may cause muscle weakness, back pain, or bowel/bladder control problems.
Some warning signs of medulloblastomas include:
- Problems with balance
- Nausea or vomiting
- Vision problems
- Problems with fine motor control, including handwriting
How Is Medulloblastoma Diagnosed?
Doctors may take several different diagnostic steps when they suspect that a patient may have a medulloblastoma.
- Neurological exam. A basic neurological exam will test a patient’s reflexes, balance, coordination, strength, vision, and hearing. This exam may prompt a doctor to look further for a tumor’s presence, and it may give a clue about the affected part of the brain.
- Imaging. Imaging technologies are non-invasive ways to look at brain tissue and possibly detect a tumor’s presence. They may also be used to judge the tumor’s size, location, and growth. Magnetic resonance imaging (MRI) uses a strong magnetic field to produce images of the brain and central nervous system. Computerized tomography (CT) scan may also be used to look for tumors.
- Biopsy. Doctors may require a biopsy, in which a sample of the tumor is removed and analyzed by a pathologist. The biopsy might be conducted with surgery or, if the tumor is in a particularly hard-to-reach area, using a needle guided by imaging technology. A pathologist’s examination of the tissue sample can help suggest the best treatment course.
- Lumbar puncture (spinal tap). This procedure is an examination of the cerebrospinal fluid (CSF). It is often performed after surgery to remove a tumor to look for signs that the growth has spread into the CSF.
How Is Medulloblastoma Treated?
Medulloblastoma treatment can vary depending on the tumor’s growth rate, location, size, and subtype.
The most direct way to treat a medulloblastoma is to remove as much of it as possible with surgical intervention. Typically, the surgery involves opening the skull and removing the tumor while not damaging the surrounding healthy tissue.
However, when a tumor has spread to other parts of the central nervous system, the surgeon may not be able to remove all of the cancerous cells. Because of this, other subsequent treatment options are usually necessary.
Surgical procedures to reduce fluid build-up in the brain are also often required.
Radiation therapies use high-energy x-rays to target and kill tumor cells directly. The radiation is typically focused on the tumor so that they do not damage healthy cells. Radiation therapy is generally necessary after surgery to remove a medulloblastoma.
Side effects of radiation therapy may include headaches, memory loss, fatigue, and scalp reactions.
Chemotherapy uses chemicals that intentionally damage the body’s cells with the expectation that healthy cells can more easily recover from the damage than tumor cells can. Chemotherapy is often used to treat medulloblastomas, particularly specific subtypes, and in cases where the tumor has spread from its original location.
How Does Medulloblastoma Progress?
The prognosis for a person with a medulloblastoma depends on several factors. Children with tumors that have not spread and are treated with surgery, radiation, and chemotherapy have a survival rate of 70-80%. However, when the cancer has spread to other parts of the central nervous system, the survival rate decreases to about 60%.
How Is Medulloblastoma Prevented?
There is no clear way to prevent a medulloblastoma from occurring.
Medulloblastoma Caregiver Tips
Caring for someone with a brain tumor can be even more challenging than the already high demands of caring for someone with any other type of severe and progressive illness. Along with the physical changes that make other cancers and serious illnesses so physically and emotionally exhausting to deal with, brain tumors also often produce psychological and cognitive changes in the patient that can threaten the caregiver’s well-being.
As you care for your loved one through the progressive stages of their illness, keep these tips in mind:
- Learn as much as possible about the potential effects of your loved one’s specific type of brain tumor. Doing so will allow you to understand how the illness affects the sufferer’s behavior.
- Get help from your friends and family. Caring for a brain tumor patient is a huge task, and you shouldn’t try to do it alone.
- Take time whenever possible to step away from the patient and the illness and find time for yourself. Acknowledge that it is normal and acceptable to need occasional relief from caregiving burdens.
- Find a support group. It can be beneficial to learn that you are not alone and that other people understand what you are going through.
Some people with brain tumors also suffer from other brain and mental health-related issues, a condition called co-morbidity. Here are a few of the disorders commonly associated with these tumors:
Medulloblastoma Brain Science
The neuroepithelial cells from which medulloblastomas grow are a type of stem cell. These cells play a crucial role in the development of the nervous system very early in the growth of an embryo. During the first weeks of embryonic development, neuroepithelial cells line the neural tube, a cylinder of cells that is an early stage in the development of the brain and spinal column.
After the neural tube is fully developed, neuroepithelial cells begin to produce a new kind of cell called a radial glial cell. These new cells then produce specialized brain cells, including nerve cells (neurons) and other cells (called glia) that support, nourish, and protect neurons.
Neuroepithelial cells continue to play an important role even after embryonic development. In the brains of children and adults, they continue to produce new neurons and glial cells as needed to support the normal function of the brain and central nervous system.
Title: Study of Stored Tumor Samples in Young Patients With Brain Tumors
Principal investigator: Amar Gajjar, MD
St. Jude Children’s Research Hospital
This laboratory study looks at stored tumor samples in young patients with brain tumors. Studying tumor tissue samples from patients with cancer in the laboratory may help doctors learn more about changes that occur in DNA and identify biomarkers related to cancer.
The overall objective of this non-therapeutic protocol is to develop and molecularly characterize patient-derived orthotopic xenografts (PDOXs), organoids, and in vitro models derived from medulloblastomas, High-Grade Neuroepithelial Tumors (HGNET), CNS embryonal tumors, Atypical Teratoid Rhabdoid Tumors (ATRTs), Choroid Plexus Carcinomas (CPCs), ependymomas, and gliomas. The investigators will characterize these models’ genome-wide mutation, expression, and epigenetic signatures and compare them with the primary tumors from which they were derived, thus creating a well-characterized and invaluable resource for research on these rare and deadly pediatric brain tumors. This will also provide important insights into intratumoral heterogeneity and molecular abnormalities that may influence the selective pressures driving evolution and tumor growth as in PDOXs, organoids, or in vitro cultures and define the relationship between these abnormalities and tumor histologic and clinical characteristics. This objective will be achieved by applying state-of-the-art DNA, RNA, and epigenome analysis tools to the study of fresh-frozen and/or cryopreserved, fixed, and cultured tumor cells, PDOXs, and organoids. The establishment of patient-derived orthotopic xenografts, organoids, and cell cultures from each tumor sample will also allow in vitro and in vivo analysis of tumor cell growth, signaling, and therapeutic response.
Title: Individualized Treatment Plan in Children and Young Adults With Relapsed Medulloblastoma (PNOC027)
Principal investigator: Sabine Mueller, MD, PhD, MAS
University of California, San Francisco
San Francisco, CA
The current study will use a new treatment approach based on the molecular characteristics of each participant’s tumor. The study will test the feasibility of performing real-time drug screening on tissue taken during surgery and having a specialized tumor board assign a treatment plan based on this screening and genomic sequencing results. This trial aims to allow every child and young adult with medulloblastoma to receive the most effective and least toxic therapies currently available and will pave the way for improved understanding and treatment of these tumors in the future.
Title: SJDAWN: St. Jude Children’s Research Hospital Phase 1 Study Evaluating Molecularly-Driven Doublet Therapies for Children and Young Adults With Recurrent Brain Tumors
Principal investigator: Giles W. Robinson, MD
St. Jude Children’s Research Hospital
Approximately 90% of children with malignant brain tumors that have recurred or relapsed after receiving conventional therapy will die of the disease. Despite this terrible and frustrating outcome, continued treatment of this population remains fundamental to improving cure rates. Studying this relapsed population will help unearth clues to why conventional therapy fails and how cancers continue to resist modern advances. Moreover, improvements in the treatment of this relapsed population will lead to improvements in upfront therapy and reduce the chance of relapse for all. Novel therapy and, more importantly, novel approaches are sorely needed. This trial proposes a new approach that evaluates rational combination therapies of novel agents based on tumor type and molecular characteristics of these diseases. The investigators hypothesize that the use of two predictably active drugs (a doublet) will increase the chance of clinical efficacy. The purpose of this trial is to perform a limited dose-escalation study of multiple doublets to evaluate the safety and tolerability of these combinations, followed by a small expansion cohort to detect preliminary efficacy. In addition, a more extensive and robust molecular analysis of all the participant samples will be performed as part of the trial to enable researchers to refine the molecular classification and better inform on potential response to therapy. In this manner, the tolerability of combinations can be evaluated on a small but relevant population, and the chance of detecting antitumor activity is potentially increased. Furthermore, the goal of the complementary molecular characterization will be to eventually match the therapy with better predictive biomarkers.