Stem Cells for Cancer Therapy
The blood-forming stem cells used for cancer therapy are called hematopoietic stem cells. They constitute less than one in 1,00,000 bone marrow cells. They look like small lymphocytes (a type of white blood cell in the vertebrate immune system) and cannot be easily distinguished.
These cells are capable of self-renewal as well as production of progenitor cells, which differentiate into mature blood cells. Bone marrow, peripheral blood (the blood returning to the heart) and cord blood (obtained from the umbilical cord at birth) are three good sources of hematopoietic stem cells.
Their number in the blood can be counted daily and collection could be done at the right time, counting the total number. Storage is done after adding special chemicals and at very low temperatures to maintain their viability for a long time.
When needed, the bag full of stem cells and additive liquid is thawed and transfused with some specific precautions (almost like a blood transfusion).
There are three major means of collecting the cells, with autologous transplant (collecting stem cells from one’s own body), allogeneic transplant transplant (collecting stem cells from someone else’s body) and syngeneic transplants, where the stem cells are collected from patient’s identical twin.
Contraindications are relative, since in many cases the risk of underlying disease is much higher.
- Age: Should not over 60 years in most cases. However, this is changing with better conditioning regimens and supportive care.
- Poor functioning of internal organs.
- Lack of a good match donor: This is slowly changing as well, with increasingly mismatched transplants now being feasible.
These transplants are done with high doses of chemotherapy and other highly immunosuppressive agents entailing risks of the same, as well as risks of graft-versus-host disease. The most common risks are related to infection, bleeding, mucositis (painful inflammation and ulceration of the mucous membranes lining the digestive tract), and chemotherapy related organ injury to the kidney, liver, lungs, etc. Mortality of transplant has reduced significantly, and is now in the range of five percent for autologous transplant and about five to 30 percent for allogeneic transplant, depending upon indication and a host factors.
The cost is mainly related to the use of:
- Blood products
- Antibiotics, antifungals etc.
- Isolation unit
- Specially trained staff
- Chemotherapy/immunosuppressive agents
- Medical investigations
- Stem cell collection
It is very difficult to calculate the cost because it differs from case to case and the type of the procedure, but roughly, for autologous stem cell transplantation, the total cost will be around five lakhs and about 10 lakhs for allogenic stem cell transplantation.
In India, we see comparatively younger patients, almost by a decade, with respect to the Western data. These are the patients who can tolerate aggressive treatments like transplant better. Newer medicines are often very expensive in India, but comparatively add a smaller increment to survival chances. For instance, to treat Non-Hodgkin lymphoma, Rituximab is a good drug, but comes at a cost of about eight lakh rupees for the course. And it does not cure relapsed lymphoma.
However, with a cost of around five lakhs, autologous transplant can cure a significantly higher number of relapsed lymphomas. This is equally true for many of the other diseases mentioned above. Thalassaemia major has a very good cure rate with transplant, and we have a very high number of this disease in India.
Research in stem cell technology is continuously improving, especially as far as the safety profiles of these therapies are concerned. Likewise, the cost for the procedure is also reducing with new research. But despite high need based on existing recommendations and patient numbers, there are very few centres in India that perform regular stem cell transplants.