What is Neuroblastoma?
Neuroblastoma is a rare cancer that develops from neuroblasts, which are the immature nerve cells, remaining after the development of the baby in the uterus. Neuroblastoma commonly affects babies and young children under the age of 5; however, older children can also be affected from it. Neuroblastoma usually develops in and around the adrenal glands. These glands have origins that are similar to nerve cells and are located on the superior part of the kidneys. Neuroblastoma can also originate in other regions, such as chest, neck, abdomen near the spine, where there are groups of nerve cells present. Neuroblastoma can also spread to other organs such as bone, bone marrow, liver, lymph nodes and skin.
Some types of neuroblastoma resolve on its own and some types will need multiple types of treatment. Treatment of neuroblastoma depends on various factors.
Causes of Neuroblastoma
The cause of neuroblastoma is not known. Neuroblastoma doesn't run in families; however, rarely it can be found in the children of the same family.
Cancer, including Neuroblastoma, generally is thought to occur because of genetic mutation where normal and healthy cells, instead of dying after a period of time, continue to rapidly divide and grow and accumulate resulting in a tumor. Neuroblastoma is a rare type of cancer which starts in neuroblasts, the immature nerve cells left behind in the uterus after the development of the fetus is complete. When the fetus reaches maturity, the neuroblasts turn into nerve fibers and nerve cells and these cells form the adrenal glands. Majority of the neuroblasts mature by the time the child is born. However, there may be some percentage of immature neuroblasts that are left behind in the newborns. Most of the times, these immature neuroblasts disappear or get mature. In rare cases, these neuroblasts form a tumor known as neuroblastoma. As mentioned before, the exact cause of the genetic mutation, which leads to the development of neuroblastoma is not clear.
Symptoms of Neuroblastoma
Symptoms of neuroblastoma depend on the origin of the cancer, which body part it has affected and whether it has spread throughout the body. Initial symptoms of neuroblastoma can be vague in nature and difficult to identify, for this reason they can be confused with some other childhood conditions. Symptoms of neuroblastoma include:
- If the patient has neuroblastoma in the abdomen, which is the commonest type, then symptoms consist of abdominal pain, lump under the skin, change in bowel habits, such as diarrhea or constipation, painful and swollen abdomen. Patient can also have difficulty in passing urine.
- Neuroblastoma in the chest produces symptoms consisting of chest pain and wheezing.
- Patient also has changes to the eyes, such as unequal pupil size and drooping eyelids. Patient also has proptosis where the eyeballs seem to protrude from their sockets.
- There are lumps of tissue present under the skin.
- Patient also experiences fever and back pain.
- Patient can have difficulty in swallowing.
- A lump can be found in the neck.
- The patient can have weakness in the legs with an unsteady walk.
- Patient can also have a limp when walking.
- There can also be numbness in the lower body.
- Bluish lumps can be found on the skin with bruising and dark circles around the eyes.
- Patient has pallor and feels fatigued.
- There is loss of appetite and weight loss.
- Patient feels pain in the bone.
- Patient feels irritable.
- Rarely, patient can have jerky muscle and eye movements.
Diagnosis of Neuroblastoma
Urine and blood test is done to look for certain chemicals that are produced by neuroblastoma cells.
Imaging tests such as ultrasound scan, CT scan and MRI scans is done of different parts of the body to view the internal structures in detail.
MIBG scan is a nuclear medicine scan where an injection of liquid radioactive substance is given, which is taken up by the neuroblastoma cells.
Biopsy also helps in confirming the diagnosis. In this test, a sample of cells or tissue is removed from the tumor and sent to lab for examination and to determine the type of cancer. Bone marrow biopsies are done to check for cancer cells in the bone marrow.
After these tests are done then the diagnosis of neuroblastoma can be confirmed and its stage can be determined.
Stages of Neuroblastoma
The stage of Neuroblastoma indicates the extent to which it has spread and the staging system for neuroblastoma is:
Stage L1: The cancer is localized and has not spread to other sites and can be easily removed by surgery.
Stage L2: The cancer is still localized to one place and has not spread; however, it cannot be easily removed surgically. The adjacent lymph nodes can also contain cancer cells.
Stage M: In this stage, the cancer has metastasized or spread to other parts of the body. This stage is considered an advanced stage.
Stage Ms: This is an advanced stage and in this stage, the cancer has spread to the liver, skin, bone marrow in children who are under 18 months old. In some babies who have neuroblastoma with this stage, the caner can also go away on its own without any treatment.
Prevalence Rate of Neuroblastoma
The incidence rate for neuroblastoma is around seven hundred cases every year, being most common among children under the age of one year. Neuroblastoma accounts for about six percent of cancer cases.
Pathophysiology of Neuroblastoma
Neuroblasts occur and migrate during the developmental phase of the fetus, which justifies the varied location of the occurrence of the condition. The underdeveloped neuroblast cells are a part of the sympathetic nervous system and having further differentiation like ganglioneuroma which are benign tumors, ganglioneuroblastoma which can be both malignant as well as benign and lastly neuroblastoma which are malignant in nature. Some neuroblastoma begins at the adrenal glands whereas some begin at the sympathetic nerve ganglia around the abdomen while the others grow around the spinal region of chest and neck.
Risk Factors of Neuroblastoma
The common risk factors that pose a threat of neuroblastoma are:
- Gender: Boys are more prone to the disease compared to girls.
- Family History: If there have been cases of neuroblastoma in past history of the family, then chances of neuroblastoma increases greatly.
- Genetic Mutations: If genetic changes occur in single nucleotide polymorphisms, then chances of neuroblastoma increase a lot.
Treatment for Neuroblastoma
The treatment for neuroblastoma is devised according to the patient depending on different factors which can affect the prognosis of the patient, such as age of the patient, cancer stage, the type of cancer cells and any abnormalities in the genes and chromosomes. Depending on all this information, the neuroblastoma is classified as low risk, intermediate risk or high risk; and depending on that, treatment plan can be a single approach or a combination of different treatment approaches.
Treatment for Neuroblastoma primarily consists of:
Surgery for Neuroblastoma: Surgery is done to remove the cancer and in some cases only surgery is sufficient as a treatment for neuroblastoma, especially in patients with low-risk neuroblastoma. Complete excision of the tumor depends on its size and location. Tumors attached to vital organs will be very risky to remove. In patients with intermediate-risk and high-risk neuroblastoma, the surgeon tries to remove as much tumor as possible after which other treatments, such as chemotherapy and radiation therapy can be done to kill any remaining cancer cells.
Chemotherapy to Treat Neuroblastoma: Chemotherapy is a treatment where chemicals are used to kill the cancer cells. In some patients, only chemotherapy can suffice for treating neuroblastoma. Chemotherapy can also be given before surgery to shrink the cancer. Patients with intermediate-risk neuroblastoma usually will be given a combination of chemotherapy drugs to shrink the tumor before surgery is done to improve the chances of removing the tumor in its entirety.
Patients with high-risk neuroblastoma will often be given intensive doses of chemotherapy to shrink the tumor and also to destroy cancer cells, which have metastasized to other parts of body. Chemotherapy is often used before surgery and before bone marrow stem cell transplant.
Radiation Therapy for Neuroblastoma: Radiation Therapy is a cancer treatment where specialized rays (radiation) are used to destroy cancer cells. Radiation therapy can be used in some patients after the surgery to kill any remaining cancer cells in the affected region. Patients with intermediate-risk or low-risk neuroblastoma can be given radiation therapy, especially if they have not benefitted from chemotherapy and surgery. Patients with high-risk neuroblastoma can also be given radiation therapy after surgery and chemotherapy to prevent recurrence of cancer.
Stem Cell Transplant: Patients with high-risk neuroblastoma are usually given Stem Cell Transplant. First they are given high-dose chemotherapy to kill the cancer cells after which a stem cell transplant is done where stem cells from the patient are collected, frozen and stored before starting the intensive chemotherapy treatment and transplanted back to the patient afterwards (autologous stem cell transplant). These stem cells later form into new and healthy blood cells.
Immunotherapy: Immunotherapy is a cancer treatment in which medication is given that directly targets only the neuroblastoma cells. The medicine used in immunotherapy works by triggering the body's immune system to fight the cancer cells. Patients with high-risk neuroblastoma can be given immunotherapy drugs.
Treatment may not be required in some cases, such as babies and infants who are lesser than 18 months old and who are in stage L1 or Ms of neuroblastoma and who do not experience any symptoms, as neuroblastoma can sometimes resolve on its own.
Complications of Neuroblastoma
Metastasis or spread of neuroblastoma to other parts of the body, such as liver, lymph nodes, bone marrow, bones and skin can cause numerous complications for the patient. Tumors which are growing on the spinal cord can compress the spinal cord resulting in pain and paralysis of the patient.
Patient can also experience additional symptoms from secretions of tumor. Certain chemicals can be secreted by the Neuroblastoma cells that cause irritation to normal tissues producing signs and symptoms, which are collectively termed as paraneoplastic syndromes.
Prognosis for Neuroblastoma
The prognosis of neuroblastoma differs from patient to patient. The prognosis is good in younger children where the neuroblastoma hasn't spread. About 50% of the patients have a type of neuroblastoma, which can return even after intensive cancer treatment. These patients will need further treatment for recurrence of cancer.
Neuroblastoma is a cancer that is typical to children under the age of five years, especially the infants. In this condition, the neuroblasts do not develop completely and multiply to form tumors which can further spread throughout the body. There are several treatments available for neuroblastoma depending upon the risk associated with it ranging from surgery, chemotherapy, immunotherapy, bone marrow transplantation to radiation therapy. A prompt treatment is usually done to increase the survival rate. However, in case of high risk neuroblastoma or advanced stages of it, the prognosis is generally average.