The high dose chemotherapy have the adverse effects on the bone marrow causing myelosupression. Usually this is followed by the blood cell recovery through the haematopoietic progenitor cells residing in the bone marrow by the complex interactions between the progenitor cells and the marrow microenvironment under the influence of various stimulatory and inhibitory factors. However, time for haematopoietic recovery is proportional to the doses and number of cycles of chemotherapy. It has been shown that chemotherapy can induce inhibitory factors such as Tumour Growth Factor (TGF)-?, Interferon(IFN)-? – IFN-?, Tumour Necrosis Factor(TNF)-? and Interleukin(IL)-4 with cytokines that causes myelosupression. HSCs are the most commonly used and they are the stem cells of choice for the haematopoietic cell transplantation following high dose chemotherapy to restore bone marrow and immune system to pre-chemotherapy levels
Some of the chemotherapeutic agents, especially alkaylating agents, should be avoided as they are reported to adversely affect stem cell yield and haemotopoietic recovery. The post-transplant period thrombocytopenia and neutropenia may be reduced by re-infusion of ex vivo expanded megacaryocyte progenitors and re-infusion of ex vivo expanded peripheral blood stem cells (PBSC) respectively. Double stem cell transplantation has been documented to improve overall survival compared to single stem cell transplantation. Granulocyte-colony stimulating factor (G-CSF) helps in proliferation and differentiation of haematopoietic progenitor cells. G-CSF has also been reported to mobilise autologous peripheral blood stem cells and to preserve and increase the length of telomerase.
Apart from long lasting replicative property of stem cells, stem cells from haemopoietic tissues seem to have ‘extraordinary’ abilities to generate or switch between haematopoietic and non-haematopoietic lineages, exhibiting an unexpected degree of developmental or differentiation potential. On theoretical grounds, this allows HSC to be used to regenerate any non-haematopoietic tissue.
In a typical stem cell transplant very high doses of chemo are used, often along with radiation therapy, to try to destroy all of the cancer. This treatment also kills the hematopoietic stem cells in the bone marrow. Without these stem cells, blood cell production would cease. Soon after treatment, stem cells are given to replace those that were destroyed. These stem cells are given into a vein, much like a blood transfusion. Over time they settle in the bone marrow and begin to grow and make healthy blood cells. This process is called engraftment.
One advantage of autologous stem cell transplant is that you are getting your own cells back. This means there is no risk that your immune system will reject the transplant or that the transplanted cells will attack or reject your body.
High-dose chemotherapy and hematopoietic stem cell transplantation has been considered to provide patients with a better chance for longer survival than other therapies.
Many factors must be considered to determine whether a patient is a candidate for high-dose chemotherapy and stem cell transplant. These include:
- The type of myeloma.
- The stage of disease and how aggressive it is.
- How the cancer responded to prior treatment.
- Age and general physical condition.