Bone Marrow Transplant - busting the myths!

The term bone marrow transplant is actually a misnomer in the present context as a vast majority of transplants are now conducted by harvesting stem cells from the blood of the donor. 

So the correct and logical term now is peripheral blood stem cell transplant. This is just like a blood donation for the donor and poses no risk at all to the donor. The term blood cancer is generally used for leukemias, these can be of two types - acute and chronic. 

For the chronic leukemias, especially chronic myeloid leukemia, stem cell transplant is now generally not required as drugs like imatinib, dasatinib and nilotinib are extremely effective. For chronic lymphocytic leukemia transplant is rarely done these days and is generally reserved for relatively younger patients. Even in the imatinib era transplant is an effective procedure and can cure patients with CML (chronic myeloid leukemia) who do not respond to imatinib and other tyrosine kinase inhibitors. 

For acute myeloid leukemias stem cell transplant is recommended for all cases except the low risk cases, after completion of chemotherapy. Risk is defined based on kind of genetic mutations in the leukemic cells for acute lymphoblastic leukemia transplant is generally done at relapse, but certain genetic mutations necessitate an earlier transplant, so does presence of or increase in minimal residual disease, which signifies cancer cells not visible to the human eye under the microscope.

Procedure of stem cell transplant HLA matching is done between patient and siblings. Best match is selected as a donor. Matched sibling is the most commonly used donor in blood cancers. In many cases a match is not available, for such cases matched unrelated donor, cord blood, or a partially matched donor (haploidentical donor) is sometimes selected. Donor is given growth factor injection subcutaneously to bring out the stem cells from the bone marrow to bloodstream, twice daily for 5 days. After that the stem cells are collected and stored. Patient is given high dose chemotherapy to kill cancer cells as well as his normal marrow. After chemotherapy, donor stem cells are injected into the body of patient from a vein. After approximately 11-14 days the donor cells get engrafted in the patient's marrow and start producing normal blood cells. The donor cells also kill the cancer cells and prevent cancer from coming back. 

Overall depending on whether the patients cancer is controlled or not before transplant the cure rate after transplant can vary from 60 % for patients who have a good control and less aggressive disease biology, to less then 20 % in patients with uncontrolled disease before transplant. Overall, approximately 40 % patients get cured with a transplant. Upto 40 % patients can develop complications, and half of these may be very severe and life threatening. This figure is more in mismatched transplants. Apart from complications, there is still a risk of relapse and these patients need close monitoring in the first few years after transplant.