14 February 2019
- Dr. Shahroch Narhwar
Cancer and the role of blood stem cell transplantation in South Africa
More than one hundred thousand South Africans are diagnosed with cancer every year (globally 14 million people).
Globally cancer kills more people than TB, AIDS and Malaria combined.
South African women life-time risk of cancer is 1:9 and for men 1:8 of which 90% are caused by the environment or life-style.
In South African women, top five cancers are breast, cervical, unknown origin, colon, Kaposi sarcoma. In men the top 5 cancers are prostate, unknown origin, Kaposi sarcoma, lung and colon. Kaposi sarcoma is almost only seen in advanced AIDS patients.
In South African women, cervix cancer is the deadliest, followed in order by breast, lung, oesophagus then colon. Cervix cancer is by far the most preventable cancer through safe sex, regular PAP smears and human papilloma virus (HPV) vaccinations in girls.
In men, this order would be cancer of the lung, oesophagus, prostate, liver and stomach.
Although blood, bone marrow and lymph gland related cancers are relatively uncommon and feature last in the top ten of all cancer deaths in South Africa (worldwide 3-5%), they are potentially curable with chemo-and radiotherapy despite being frequently wide-spread at time of diagnosis.
Blood/ bone marrow and lymph gland cancers are ideally treated by haematologists (blood specialists) while other (solid tumour) cancers are treated by oncologists (cancer specialists).
Blood/bone marrow and lymph gland cancer survival rates have more than doubled over the past thirty years in stark contrast with dismal survivals of oesophagus, stomach, lung, pancreas and brain cancer which have not improved over this time period.
Moreover, lymph gland (lymphoma) cancers are common in AIDS patients together with Kaposi sarcoma, both exclusively treated with chemo-and radiotherapy and antiretroviral therapy. South Africa has got the highest number HIV positive individuals in the world.
In children, acute lymphoblastic leukaemia is the most common cancer and also in the top 5 most curable cancers together with lymph gland cancers, germ cell and kidney tumours.
Blood, bone marrow and lymph gland related cancers are also frequently treated with high dose chemo-and radiotherapy followed by blood (bone marrow) stem cell transplants, especially for high risk or relapsed disease.
The high-dose chemo-and radiotherapy is the conditioning or preparative regimen to clear microscopic cancer (that may be left behind after conventional dose chemo-and radiotherapy) and empty the bone marrow to make space for the collected blood (bone marrow) stem cells.
These bone marrow/blood stem cell transplants are preferentially:
1. autologous (patient is both donor and recipient) for lymph gland cancers or
2. allogeneic (donor is somebody else) for bone marrow cancers where the patient s immune system is replaced by the donor's immune system, suited to attack the cancer.
Allogeneic stem cell transplantations are also performed for benign haematological conditions like bone marrow failure syndromes, thalassaemia and sickle cell anaemia, treatment-resistant autoimmune diseases like scleroderma or multiple sclerosis and rare metabolic and immune disorders in children. Here the function of the blood (bone marrow) transplant is rather to replace the missing or faulty bone marrow.
For the past 20 years peripheral blood rather than bone marrow is most often used of which the stem cells are being harvested though a apheresis machine which separates these cells from the blood returned to the body after stimulating the bone marrow with under the skin injections of white cell growth factor.
Allogeneic blood stem cells originate from a suitable donor and ideally belong to a sibling donor (25% chance of full tissue match) compared with a less than 1:10000 chance to find a random full donor match for a Caucasian patient and less than 1:100000 chance to find a random full donor tissue match for a mixed-race patient (unrelated voluntary donors).
In addition, finding and obtaining unrelated blood or bone marrow stem cells from voluntary donors is often time-consuming, very costly and most often not accessible to the more than 90% (medically uninsured) South African population.
For the past decade however, haematologist have developed the haplo-identical transplant technique with half-matched family donors which makes it possible to transplant almost all patients in need for a blood stem cell transplant. This technique is both feasible and cost-effective but most importantly accessible to most patients in dire need for a potentially curative procedure for an otherwise fatal blood/bone marrow or lymph gland disease.