Neuroblastoma is a form of cancer that starts in certain types of very primitive nerve cells found in an embryo or fetus. (The term neuro refers to nerves, while blastoma refers to a cancer that affects immature or developing cells). This type of cancer occurs in infants and young children. It is rarely found in children older than 10 years.
A little more than 1 out of 3 neuroblastomas start in the adrenal glands. About 1 out of 3 begins in sympathetic nerve ganglia in the abdomen. Most of the rest start in sympathetic ganglia near the spine in the chest or neck or in the pelvis.
Key statistics about neuroblastoma
Neuroblastoma is by far the most common cancer in infants (less than 1 year old). It accounts for about 7% of all cancers in children. There are about 650 new cases of neuroblastoma each year in the United States and 300 in Canada. This number has remained about the same for many years.
The average age at the time of diagnosis is about 1 to 2 years. In rare cases, neuroblastoma is detected by ultrasound even before birth. Nearly 90% of cases are diagnosed by age 5. Neuroblastoma is extremely rare in people over the age of 10 years.
In about 2/3 of cases, the disease has already spread (metastasized) to other parts of the body when it is diagnosed.
Risk factors for neuroblastoma
A risk factor is anything that affects your chance of getting a disease such as cancer. Different cancers have different risk factors.
Lifestyle-related risk factors such as diet, body weight, physical activity, and tobacco use play a major role in many adult cancers. But these factors usually take many years to influence cancer risk, and they are not thought to play much of a role in childhood cancers, including neuroblastomas.
No environmental factors (such as exposures during the mother’s pregnancy or in early childhood) are known to increase the chance of getting neuroblastoma.
Neuroblastoma is most common in very young children, but it is still rare even in this age group.
In rare cases (about 1% to 2% of all neuroblastomas), children may inherit an increased risk of developing neuroblastoma. But the vast majority of neuroblastomas do not seem to be inherited.
Pathology and staging of neuroblastoma
When neuroblastoma has been diagnosed, tests will be done to find out:
- how aggressive the tumour is
- the stage of the cancer (how far the cancer has progressed)
How well the cancer responds to treatment (the prognosis) depends on:
- the age of the child
- the stage of the cancer
- the MYCN status
- MYCN is a gene that controls cell growth. A single copy of the gene is normal and is associated with a less aggressive form of neuroblastoma.
- the amount of DNA in each cell (DNA ploidy)
- Neuroblastoma cells that have more DNA are often associated with earlier stages of disease, tend to respond better to treatment and usually have a better outlook.
- tumour histology (what the cells look like under a microscope and how they behave)
- The more cancer cells look like normal cells, the more controlled they behave and the better the prognosis.
The above factors are used to classify a child’s neuroblastoma into a risk category. High-, intermediate- or low-risk classifications help determine the child’s prognosis and plan the best treatment approach.
The 5-year survival rate in children in the high-risk group is around 30%.
Treatment for neuroblastoma
Treating neuroblastoma is complex and often requires the expertise of many different doctors, nurses, and other health professionals. Pediatric oncologists, surgeons, radiation oncologists, and oncology nurses will get together to plan the most effective treatment.
The approach to treatment of neuroblastoma depends on the stage of the cancer, the child’s age, and other factors such as prognostic markers. The types of treatment used may include:
- Retinoid therapy
- Radiation therapy
- High-dose chemotherapy/radiation therapy and stem cell transplant
In many cases, more than one type of treatment is needed.