Results of Bone Marrow Transplantation
The outcome of BMT depends on four factors
- Fitness of the patient
- Choice of conditioning
- Choice of Donor
- Nature of Disease
Fitness of the Patient
The ability of various organs of the body to withstand the assault of high dose chemotherapy is the key to the success of BMT. We can assess the suitability of the patient to undergo a particular type of conditioning by several scoring systems such as HCT-CI (Haematopoietic Cell Transplantation – Co-morbidity Index). For example, if the HCT-CI score is 0, the chance of transplant related mortality is only 10%. On the other hand, if the HCT – CI score is 3, the chance of transplant related mortality is 40%.
Choice of Conditioning
The aim of conditioning is to eliminate the diseased bone marrow, whether it is leukemia or Thalassemia. In addition, the patient’s immune system needs to be dampened, so that the donor cells are not rejected.
The backbone of conditioning has been total body irradiation. However, this has a lot of short and long term side effects, especially in children. Hence, only chemotherapy based conditioning has been developed particularly for children.
Over the last decade, several ground breaking researches have shown that high dose chemo-radiotherapy might not be essential to prevent rejection or eliminate leukemia, when the patient has low disease burden. This is called REDUCED INTENSITY CONDITIONING (RIC). The Results of RIC in most conditions are similar to conventional conditioning.
In older patients, we prefer RIC. In younger patients and in those with high risk leukemia or lymphoma, conventional conditioning is preferred.
Choice of Donor
Matched Family Donor is always the preferred choice irrespective of all other conditions. However, only 20% of patients have a matched family donor.
The other donors are called alternative donors and are as under :
- Matched or Mismatched unrelated donor from Volunteer Registries
- Matched or Mismatched Unrelated Cord Blood Unit from Public Cord Blood Banks
- Half Matched Family Donor (Haploidentical)
Nature of Disease
It is now well established that the chances of success are highest if a patient with leukemia undergoes BMT when the disease is in remission (not detected by routine testing). When leukemia recurs, the chances of cure are reduced by 50 – 80%, even with BMT. In addition, certain leukemia are at high risk of relapse because of the aggressive nature inherent in the chromosomes of the cancer cells.
Similarly, the best results in non malignant diseases such as Thalassemia, Sickle Cell Anaemia and Aplastic Anaemia are obtained when they are transplanted early.