Stems Cells as a Cancer Treatment

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Within marrow tissue found in the center of bones, the body produces red and white blood cells, which are critical to transporting oxygen and fighting off infection. Certain types of cancers can cause serious damage to bone marrow, leaving patients without the blood cells needed to perform these important functions. Using stem cells from either the patient or a donor, doctors can now replace this tissue and allow patients to begin forming their own blood cells again. This procedure, which is known as a bone marrow or stem cell transplant, can be lifesaving for cancer patients.

Stem cells are cells within the body that can grow to serve as most other types of cells. They serve as a natural repair system for the body, allowing it to replace cells that are damaged beyond repair. Adult stem cells are commonly found in bone marrow and can be used to create new bone marrow tissue. Once implanted within bone marrow, the stem cells divide and modify themselves to form specific functions.

Stem cell transplants are most often used for patients with leukemia and lymphoma, cancers that directly attack bone marrow tissue. They can also be used to replace bone marrow damaged by very high doses of chemotherapy and radiation therapy used to treat other cancers. Once the patient receives an initial high dose of radiation or chemotherapy, they can then begin to receive the transplanted stem cells. The stem cells are injected directly into the patient’s bloodstream through an IV. Once inside the bloodstream, the stem cells then make their way to the damaged bone marrow tissue and begin to implant and grow. Over several months, the body begins to form new blood cells. It can take several months for red blood cell counts to be replenished, and up to two years for the immune system to fully recover.

Stem cell treatments fall into two specific categories depending on the source of the new cells. In autologous transplants, the cells come from undamaged tissue in the same patient. This technique is often used on cancers that do not directly attack the bone marrow tissue. Before chemotherapy or radiation therapy, bone marrow tissue is taken from the patient. Once this initial therapy is complete, the tissue then can be injected back into the patient, allowing the bone marrow to regenerate. Autologous transplants are preferable in many circumstances since the body recognizes the newly introduces tissue and does not mount an immune response as a result.

However, in cases of cancer such as leukemia that attack marrow tissue, patients may not have undamaged marrow tissue to collect. In these cases, a transplant from another donor becomes necessary. These cases are known as allogeneic transplants. In an allogeneic transplant, patients are matched with donors by human leukocyte antigen (HLA) type. HLA are proteins that exist on most of the body’s blood cells and help the body distinguish normal cells from foreign ones. Having a similar marker reduces the chances that the patient’s immune system will reject the cells, a condition known as Graft versus host disease (GVHD).

For an allogeneic transplant, a patient’s blood is first sampled to determine the HLA type. The patient is then matched with a donor, a process that can take several weeks. While the best donor is generally an immediate family member, 75% of patients do not have a suitable donor in their family and require an unrelated donor. These donors can be located through national registries such as the National Marrow Donor Program.

Stem cell transplants play an important role in treating cancers that damage bone marrow as well as in complimenting other types of cancer treatments by mitigating harmful side effects. Using modern technology, these transplants can be completed quickly and minimally invasively. Although the recovery process can be long, stem cell transplants allow many patients to eventually resume normal, healthy lives.

References:
https://www.mdanderson.org/treatment-options/stem-cell-transplantation.html
https://www.cancer.net/navigating-cancer-care/how-cancer-treated/bone-marrowstem-cell-transplantation/what-bone-marrow-transplant-stem-cell-transplant
https://www.webmd.com/cancer/cancer-stem-cell-treatment#1
https://www.cancerresearchuk.org/about-cancer/cancer-in-general/treatment/bone-marrow-stem-cell-transplants