The incidence of recurrence of leukemia in donor cells after allogeneic bone marrow transplantation.

A total of 243 patients with acute leukemia received a marrow graft from a donor of the opposite sex. Seventy-five patients subsequently relapsed, and specimens of the recurrent leukemia cells were available for cytogenetic analysis in 54. Three relapses were in donor-type cells. Four patients whose relapses were in host-type cells showed a cytogenic abnormality that differed from the original leukemic clone. We conclude that a 'new' leukemia in donor cells, and possibly in host cells, constitutes a small but significant fraction of recurrent leukemia after marrow grafting.