Why is a stem cell transplant necessary?
There are many reasons stem cell transplants are offered. This treatment can provide normal stem cells to patients:
- Whose own stem cells stem cells are abnormal, absent or defective
- Whose own stem cells has been destroyed by chemotherapy and radiation therapy in order to treat cancer
- Whose genetic disease affects organs in the body
A stem cell transplant usually requires the treatment of high doses of chemotherapy or radiation which will kill the patients stem cells and then replace or rescue the patient with donor cells. Depending on your child’s diagnosis, it may be necessary to use a less toxic chemotherapy protocol, called sub-myeloablative transplant. The purpose of the sub-myeloablative transplant is to allow gradual engraftment of the donor’s cells with subsequent progressive replacement of the host's own cells and immunity. The patient may develop full donor chimerism without the long period of waiting for engraftment and with less of the associated toxicity.
The following is a list of some diseases or disorders treated by a stem cell transplant
Leukemia. This is a cancer of white blood cells that develops in the stem cells. This cancer causes an abnormal growth of white blood cells which crowd out the other normal blood cells. These abnormal white blood cells remain young or immature and are ineffective. The stem cells cannot produce red blood cells, platelets, or normal white blood cells. A stem cell transplant is necessary to treat these cancers so that healthy normal blood cells can replace the ineffective cells. There are different types of leukemia usually associated with different types of white blood cells. Common types of leukemia include:
- Acute Lymphocytic Leukemia (ALL) is the most common cancer of blood in children. It affects the lymphocytes.
- Acute Myelogenous Leukemia (AML) is also called acute myelocytic leukemia. It affects the granulocytes.
- Chronic Myelogenous Leukemia (CML) is a slowly progressing form of leukemia that is more common in adults than in children. It also affects the granulocytes.
Solid tumors. Transplants can also been used to treat a variety of malignant solid tumors such as neuroblastomas, lymphomas, and brain tumors. Unlike the leukemias, these types of cancer may not directly affect the patient’s stem cells. This is why an autologous transplant (where the patient receives his or her own stem cells) may be used to treat these tumors. The treatment of solid tumors may require extremely high doses of chemotherapy and radiation, higher than can be given with standard chemotherapy regimens. The patient’s stem cells are damaged and unable to recover. The transplant is given as a stem cells rescue. In this case, some of the patient’s stem cells are removed before the treatment begins and are frozen. The child receives high doses of chemotherapy and radiation which is intended to kill the tumor. The frozen stem cells are then thawed and returned to the patient.
Aplastic anemia. Children with this disease are lacking all types of blood cells because the stem cells no longer functions. Fevers and infections develop because there are not enough white blood cells to fight off bacteria or viruses in the body. Patients may bruise or bleed easily because there are not enough platelets to help the blood clot. The patient may tire easily because he/she is anemic, which means there are not enough red blood cells to carry oxygen throughout the body.
Sickle cell disease/thalessemia. Sickle cell disease is characterized by red blood cells that assume an abnormal, rigid, sickle shape. Sickling decreases the cells' flexibility and results in their restricted movement through blood vessels, depriving tissues of oxygen. With transplantation, patients receive normal stem cells which allows the production of all types of blood cells again. Thalessemia is caused by a genetic defect that results in a decreased rate of production of one of the globin chains that make up hemoglobin. Reduced production can cause the formation of abnormal hemoglobin molecules and this in turn causes the anemia which is the characteristic presenting symptom of the Thalassemia.
Inherited metabolic diseases. These diseases are caused by a malfunctioning or missing gene that causes severe defect in certain chemical pathways. This can result in the collection of abnormal material in the liver, spleen, brain and lungs. These diseases include Hurler’s Syndrome, Adrenoleukodystrophy and Metachromatic Leukodystrophy. With transplantation, patients receive normal stem cells which allows for the production of the missing gene or replace the malfunctioned one.
Immune disorders. These diseases are caused by a missing or malfunctioning T lymphocyte cells in the immune system. These diseases include severe combined immunodeficiency disease (SCID) and Wiskott - Aldrich syndrome. After transplantation, the patient’s new stem cells produces properly functioning T cells which create an effective immune system.
Common diseases treated by transplant
- AML - Acute myelogenous leukemia
- ALL - Acute lymphoblastic leukemia
- APL- Acute Biphenotypic leukemia
- CML - Chronic myelocytic leukemia
- JCML - Juvenile chronic myelocytic leukemia
- MDS - Myelodysplastic syndrome (pre-leukemic syndrome)
- Ewing’s Sarcoma
- PNET (brain tumor)
- Severe Combined Immunodeficiency syndrome (SCID)
- Wiskott Aldrich syndrome (WAS)
- Blackfan Diamond Syndrome
- Hurler’s Syndrome
- Chronic Granulomatous Disease (CGD)
- Hyper IgM Syndrome
- Aplastic Anemia
- Fanconi’s anemia
- Thalassemia major
- Glanzmann’s Thrombasthenia
- Sickle cell anemia