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Biomedical Research

Changing Our Understanding of Medulloblastoma

Medulloblastoma is a common form of cancer among children. The research team at St. Jude Children’s Hospital sought to find out why one-third of children relapse.

By Kyle Phong

Published 11:16 PM EST, Mon March 1, 2021

Introduction

At St. Jude Children’s Research Hospital, scientists conducted the largest analysis of primary and relapsed medulloblastoma tumors to date. The research team divided medulloblastoma into four molecular groups: WNT, SHH, (both named after their genetic mutation), Group 3, and Group 4.  Upon discovering that about one-third of these patients relapsed and displayed a five-year survival rate of 10%, the researchers sought to find out why this was occurring.

What is Medulloblastoma?

Currently, medulloblastoma is the most commonly found brain tumor in children younger than 16 years old.  If it is not detected early and treated, it tends to spread to other areas of the brain as well as the spinal cord. The specific cause of medulloblastoma is not known, but cancer is formed due to the uncontrolled, rapid division of a mutated cell. A small percentage of childhood medulloblastomas are hereditary.  

Symptoms: Typical symptoms for a child with medulloblastoma are worsening nausea and vomiting, clumsiness, headaches, and seizures.  If cancer has metastasized to the spinal cord, the child might also experience problems walking, back pain, and difficulties with controlling their excretory functions.  

Survival Rate: Assuming the tumor has not spread, the survival rate is 70-80%, which is fairly high compared to several other cancers. If it has spread to the spinal cord, the rate lowers to about 60%.  

Treatment: The three main treatments of medulloblastoma are surgery, radiation, and chemotherapy. During surgery, as much of the tumor is removed as possible without jeopardizing the patient’s health.  Depending on how much of the tumor is left, the patient then undergoes radiation therapy and chemotherapy. Radiation therapy is when high radiation such as X-rays kills cancer cells. Chemotherapy is a medicine that is injected or orally consumed to kill cancer cells. 

Research and Data Analysis 

In the study, each of the four groups of medulloblastoma was then organized by their five-year survival rate. WNT tumors have a 95% five-year survival rate, SHH and Group 4 have about a 75% five-year survival rate, and Group 3 has a 60% five-year survival rate. Next, the research team analyzed data from two trials, SJMB03 and SJYC07. SJMB03 includes international children with newly diagnosed medulloblastoma from 2003-2012.  SJYC07 includes children younger than 3 years old with newly diagnosed medulloblastoma. They found that approximately one-third of patients either experience treatment failure or relapse, which is when cancer returns, and only 10% survive past five years post relapse.  

Further analysis of results revealed that about 10% of these relapsed medulloblastomas were wrongly classified. These were actually secondary malignancy which is cancer caused by radiation or chemotherapy. These secondary cancers manifest as high-grade gliomas, which are aggressive and incurable. High-grade gliomas and relapsed medulloblastoma have different treatments, therefore patients who were misclassified received incorrect medicine.  

Researchers found that medulloblastomas typically stay in the same molecular group when relapsed, but there has been evidence of some switching from Group 3 tumors to Group 4.  Despite this evidence, the research team learned that most of the time, tumors are genetically stable. Using whole-exome sequencing, they found patterns of relapse in childhood medulloblastoma.

Conclusion

Dr. Robinson, an oncologist at St. Jude, states that this research provided a better understanding of medulloblastoma and its risks. Depending on the type of medulloblastoma, we are able to determine a more precise amount of, along with the specific type of therapy needed for the patient. Now able to better understand these tumors, treatment of relapsed medulloblastoma may significantly improve. 

Kyle Phong, Youth Medical Journal 2021

References

Journal of Clinical Oncology, “Clinical Outcomes and Patient-Matched Molecular Composition of Relapse Medulloblastoma”, 27 January 2021

https://ascopubs.org/doi/10.1200/JCO.20.01359

News Medical Life Sciences, “New results challenge the current understanding of medulloblastoma”, 28 January 2021

https://www.news-medical.net/news/20210128/New-results-challenge-the-current-understanding-of-medulloblastoma.aspx

St. Jude Children’s Research Hospital, “Medulloblastoma”

https://www.stjude.org/disease/medulloblastoma.html

Together Powered by St. Jude Children’s Research Hospital, “Medulloblastoma in Children and Teens”

https://together.stjude.org/en-us/about-pediatric-cancer/types/brain-spinal-tumors/medulloblastoma.html

National Cancer Institute Center for Cancer Research, “Medulloblastoma Diagnosis and Treatment”

https://www.cancer.gov/rare-brain-spine-tumor/tumors/medulloblastoma

By Kyle Phong

Kyle Phong is a student at Whitney High School in Cerritos, California. He enjoys learning about the fields of psychology and evolution.

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