How Stem Cell Treatments Work for Cancer
In patients with leukaemia treated with chemotherapy and stem cell transfusion the graft-versus-tumor (GVT) effect that happens after allogeneic bone marrow or peripheral blood stem cell transplant is part of the overall effectiveness of the treatment. GVT happens when the donor white blood cells target and destroy the remaining cancer cells in the patient’s body after chemotherapy. Graft-versus-host disease is also a possible complication however, although this is much better managed than ever before. The two main types of cancer treatment where stem cell transplants are used are leukaemia and lymphoma and the treatment is most effective when the cancer is in remission. Other cancers, such as neuroblastoma, and multiple myeloma, are also treated with stem cell transplants and a number of other cancer types are being investigated in clinical trials for their response to stem cell therapy.
Stem Cell Donors for Cancer Treatment
Adult stem cells and umbilical cord stem cells are the only ones currently used for cancer treatment and these must be matched to the patient as closely as possible in order to reduce the risk of rejection. The way that the doctors do this is by testing the HLA antigens (sets of proteins) on the surface of the stem cells of both donor and patient by a blood test. The success of an allogeneic transplant often depends on how closely matched these HLA antigens are as this reduces the risk of GVHD. Only 25-35% of patients requiring transplant have a sibling with matching HLA antigens, making this type of transplant less common than one from an unrelated donor. Many countries encourage those from minority ethnic and racial groups to donate stem cells, from cord blood, peripheral blood, or bone marrow, as the chances of finding an HLA-matched donor increase when donor and recipient are of similar backgrounds and these groups are usually underrepresented in blood banks.
Screening Donated Stem Cells for Cancer Cells
When an autologous stem cell transplant takes place as part of cancer treatment the harvested cells are tested for, and sometimes purged of, cancer cells. This minimizes the risk of the cancer coming back but also reduces the number of healthy stem cells meaning that more stem cells are usually taken initially than are likely to be needed in the treatment to accommodate such losses. Stem cells transfused into the patient will travel to the bone marrow and begin to produce new red and white blood cells along with platelets, thereby restoring the patient’s immune system, allowing more oxygenated blood to be carried around the body, and reducing the risk of bleeding by facilitating proper clotting. This occurs during a process called engraftment which usually takes 2-4 weeks after the transplantation and which is monitored by regular blood counts. Whilst the red blood cells and the platelets recover fairly quickly from such treatment, the body’s immune system can take months, or even years, to recover fully leaving the patient vulnerable to infection. Patients receiving an autologous stem cell transplant for their cancer will usually recover immune function faster than those having an allogeneic or syngeneic transplant which can take 1-2yrs for complete recovery.
Read More –> Side-Effects of Stem Cell Cancer Treatment
