Second Transplant due to Relapse
Generally, outcomes of second transplant in leukemia patients after relapse of a 1st Allo-HSCT transplant are poor with low rates of disease free survival (~14%). aGvHD is frequently involved. Outcomes in non-malignant diseases such as AA a slightly better at around 40%.
Where a second transplant is being considered, the return of full patient haematopoiesis must be confirmed by chimerism studies. High/allele resolution patient HLA typing post relapse should be undertaken to confirm patient HLA typing has reverted to their original type and is not that of the donor type.
The donor identification strategy will be determined by the urgency of the transplant and should always be discussed with the stem cell team. If there are any 12/12 sibling prepared to donate this should be considered. If the stem cell unit have experience of haplo identical transplants, then donation from a sibling or parent could be a good option. A re-search of the adult and cord blood registries should be undertaken to determine if there are any new donors that may be 12/12. If there are no new donors, it may be possible to re-use the previous donor, depending on the reasons for the relapse. For instance, if the relapse was due to low cell harvest, it may be possible to do a bigger collected for the 2nd transplant.
A key consideration for second transplant is the induction and immunosuppression strategy which may be different from the 1st transplant.
Second Transplant due to Donor Derived Leukemia
Chimerism studies should be undertaken to confirm the patient retains 100% donor chimerism and therefore that the leukemia is indeed donor derived. In this scenario going back to the original donor for a second harvest is not an option. There is a duty of care to inform the registry who may want to contact the donor as the donor may currently be asymptomatic and may need counselling a treatment themselves.
Donor options available to the patient for a second transplant depend on clinical urgency and need to be discussed with the stem cell team. If a 12/12 sibling or other related donor is available then this is a potential option. In conditions where haplo identical transplants are a clinical option then this can be considered. A search of the international stem cell adult and cord blood registries should be initiated early in case there are no related donors.