Stem Cell Cancer Treatment – Side-Effects
Those chemotherapy for cancer are at increased risk of infection and bleeding during the period in which the transplanted stem cells are rebuilding the body’s levels of red and white blood cells, and platelets. A patient may, therefore, be given antibiotics in order to prevent and infection occurring or to treat an infection if it arises. Patients may also be given platelet transfusions and red blood cells to prevent bleeding and anaemia. Chemotherapy and stem cell transplants also cause short-term side-effects including nausea and vomiting, fatigue, appetite loss, hair loss, mouth sores, and skin problems in some patients. These symptoms are usually short-lived however but there are longer term problems to consider in addition to these. Chemotherapy and radiation therapy can lead to infertility, cataracts, liver, kidney, heart, lung, and other organ damage, and secondary cancer in a few cases. For many patients they may consider storing eggs or sperm prior to cancer therapy if they are thinking about having children at a later date.
Graft-Versus Host Disease
Graft-versus-host disease is a potential complication of stem cell therapy for cancer as the white blood cells from the donated blood (the graft) may determine cells in the recipient’s body to be foreign and launch an attack against them, just as the body’s immune system would do were it to encounter a virus or infectious agent (in most cases). If GVHD develops then those organs at most risk include the skin, liver, and intestines and the condition will usually materialize within a matter of weeks of the stem cell treatment although it can also occur at a later date. Immunosuppressant drugs may be used where the donor stem cells are not an ideal match for the patient in order to reduce the chance of GVHD occurring. The donated stem cells may also b treated to remove the white blood cells (T cells) prior to transplantation although this may make the stem cell transplant less efficacious than a better matched transfusion. GVHD is treated with steroids and other immunosuppressants but can be very difficult to address. The good news however is that patients who experience GVHD have less likelihood of their cancer returning as the white blood cells are likely to seek and destroy those remaining cancer cells more efficiently.
Alternatives to High-Dose Chemotherapy
A fairly new procedure is currently being studied in clinical trials to determine its efficacy and safety for those with cancer. Known as a ‘mini-transplant’, reduced-intensity transplant, or a non-myeloablative transplant the technique may be effective for leukaemia, lymphoma, multiple myeloma, and a number of other cancers of the blood. Lower doses of chemotherapy and/or radiation are used initially and then the patient receives an allogeneic transplant of stem cells. The lower dose cancer therapy means that some cancer cells are likely to remain, along with some of the patient’s own bone marrow stem cells which allows for a faster repopulation of their immune system and blood-forming cells. The chemotherapy and/or radiation also suppress the patient’s immune system and as the donor stem cells begin to engraft a graft-versus-tumor effect may occur which causes the donor stem cells to destroy the remaining cancer cells. Patients may also be given an infusion of the donor’s white blood cells (leukocytes) to increase this GVT effect in a procedure known as donor lymphocyte infusion.
Tandem Transplants – Stem Cells Cancer Therapy
Tandem transplants are also under investigation in clinical trials as an alternative method of autologous stem cell transplant for cancer patients with multiple myeloma or germ cell cancer. Two courses of high-dose chemotherapy are used in this procedure with a few weeks or months in-between and with stem cell transplants afterwards. This is hoped to lower the risk of the patient’s cancer returning following treatment.
Cancer Stem Cell Research
Stem cells are also being used to investigate the behaviour of cancers in the laboratory in order to determine the origins of some cancers and develop new, targeted, treatments. Corsten (et al, 2008) observed that the tumoritropic migratory properties of stem cells (i.e. they hone in on cancer cells in the body) could provide an effective method of delivering targeted treatment to tumors and in cases where the cancer has metastasized. Laboratory work has demonstrated that it is possible to specifically alter stem cells’ genes to exert an antitumor effect, encourage localized immune response, oncolytic virus production and pro-drug activation. In animal studies this appears to be a safe and effective technique for targeted anti-cancer treatment delivery. Intra-cranial tumors are one area in which this kind of stem cell treatment looks likely to provide a promising alternative to current strategies. Brain cancer is difficult to treat in most cases as it spread rapidly and any treatment risks damaging nearby healthy tissue.
Neural Stem Cell Transplants and Brain Cancer
In one study at Harvard Medical School, rats who had been given intra-cranial tumors were then given human neural stem cells transplants. The researchers observed the migration of the stem cells to the site of the tumor and the subsequent production of cytosine deaminase. The cytosine deaminase is an enzyme which creates a chemotherapeutic substance from a non-toxic pro-drug, thus reducing the size of the tumor by 81% in these rats. The stem cells did not differentiate, nor did they become tumorigenic, which is a worrisome possibility of stem cell treatments for cancer and other diseases and conditions. This particular treatment would be favorable in comparison to chemotherapy and radiation as it is apparently able to discriminate between cancerous cells and healthy cell types thereby reducing the side effects of treatment and ‘collateral damage’.
Continue Reading –> Cancer Stem Cells
References
Corsten MF, Shah K., Therapeutic stem-cells for cancer treatment: hopes and hurdles in tactical warfare, Lancet Oncol. 2008 Apr;9(4):376-84.
Klopp AH, Gupta A, Spaeth E, Andreeff M, Marini F 3rd., Concise review: Dissecting a discrepancy in the literature: do mesenchymal stem cells support or suppress tumor growth? Stem Cells. 2011 Jan;29(1):11-9. doi: 10.1002/stem.559.
