Sometimes it affects more than one site.
More treatment using chemotherapy is required to get the leukaemia into remission.
With some types of relapse, further chemotherapy treatment is the best option. For relapses which occur during the treatment or soon after stopping it, bone marrow transplant from a matched family member will be undertaken provided that second remission has been achieved. In children who do not have a matched family bone marrow donor, chemotherapy or, more recently, using bone marrow from a matched unrelated donor may be considered. The latter is still regarded as experimental therapy and although early results are encouraging, there are more risks from this procedure than with chemotherapy or using a matched family donor. Finding a matched unrelated donor takes about 3-4 months to be completed and a suitable donor is usually found for about half of the patients.