My general knowledge about stem cell transplants was challenged recently when I was asked questions about the procedure. I was embarrassed to say I didn’t know, and was thus motivated to do some reading and fill the information void I had acknowledged. You hear about stem cell and bone marrow transplants all the time and as a physician, people expect me to know something about them. Well, I knew only the bare minimum, so what follows is information I learned from several reliable sources.
Stem Cells are specialized cells that can mature into many other kinds of cells, depending on what your body needs. They are located in various places in the body. Most stem cells are found in the bone marrow, the tissue occupying the space in the center of larger bones, where new blood cells are formed. Here, stem cells mature into red blood cells (carry oxygen to the body tissues), white blood cells (fight off infections), and platelets (initiate blood clots and wound healing).
Stem Cell and Bone Marrow Transplants are basically the same procedure, it’s just that the stem cells originate from different sites. In a stem cell transplant, stem cells are taken from your circulating blood, or that of a donor, and in bone marrow transplants, stem cells are taken from your bone marrow or a donor’s. In either circumstance, stem cells are separated from other cells by a process called apheresis. Blood is taken, as would be done at a blood donation center, then processed to remove the desired type of cells. Those cells are then frozen and stored until needed.
Stem cell transplants are done as part of treatment for:
Acute and Chronic Leukemia
Aplastic Anemia
Bone Marrow Failure
Hemoglobinopathies
Hodgkin’s Lymphoma
Immune Deficiencies
Multiple Myeloma
Myelodysplastic Syndromes
Neuroblastoma
Non-Hodgkin’s Lymphoma
Plasma Cell Disorders
Testicular Cancer
Lupus, Crohn’s Disease, Multiple Sclerosis, Systemic Sclerosis
Myasthenia Gravis
Two types of stem cell transplants are done:
Autologous stem cell transplant—your own stem cells are given to you like a blood
transfusion. The patient receives his/her own cells so there is no worry about
rejection.
Allogenic stem cell transplant—the patient receives stem cells from a donor whose
tissue type closely matches the recipient’s.
The procedure to “transplant” stem cells into a patient is the same as a blood transfusion. Thawed stem cells are administered intravenously to the patient after receiving high doses of radiation therapy or chemotherapy. Donor stem cells make their own immune cells which help to kill any cancer cells that remain after high dose treatment. Because chemo wipes out the immune system, it takes about 6-12 months for the immune system to recover and begin producing healthy new blood cells. This a time of serious concern about rejection (Graft vs. Host Disease) and infection. Precaution and prophylactic antibiotics are important.
In summary, stem cells are specialized cells found in the blood and bone marrow, that develop into whatever type of cell the body needs. Most often they become components of circulating blood—red blood cells, white blood cells, and platelets. Transplanting stem cells is beneficial in treating several types of cancer; most often leukemias and lymphomas. A patient may receive his own, or a donor’s, stem cells in the form of an intravenous infusion. After a high dose radiation treatment or chemotherapy that kills any remaining cancer cells, stem cell are infused IV. The patient’s response to treatment is monitored closely for 6-12 months in anticipation of a response.
Statistics to evaluate the success of stem cell transplantation are difficult to generalize because they differ from one cancer type to another. However, when given for multiple sclerosis, at five years there was an overall survival rate of 93% and 50% of patients had no progression of their disease. For multiple myeloma I saw the following stats: 79% survival at 3 years, 81.2% at 5 years depending on the source. These are better than outcomes for those without stem cell transplant so the procedure has found a significant niche in cancer treatment, in particular, and non-cancer disorders as well.
References: https://www.mdanderson.org/treatment-options/stem-cell-transplantation.html
