Anti-leukemic effect of graft-versus-host disease on bone marrow and extramedullary relapses in acute leukemia

Several reports have suggested that the graft-versus-leukemia effect at extramedullary (EM) sites might be less prominent than that in the bone marrow (BM). We analyzed the effect of graft-versus-host disease (GVHD) on BM and EM relapses in 194 consecutive patients with acute leukemia who underwent allogeneic hematopoietic cell transplantation at a single institute.

We compared relapse-free survival (RFS), BM RFS, and EM RFS after allografting according to the occurrence of GVHD. We also investigated the clinical outcome of patients who relapsed after their allogeneic transplantation.

Relapse occurred in 65 patients; in 41 (63%) relapse occurred in the BM only, in 9 (14%) it occurred in both BM and EM sites, and 15 (23%) in EM sites only. Patients who developed acute GVHD after transplantation had significantly higher relapse-free survival (69.2% vs. 52.4%; p=0.042) and BM RFS (80.7% vs. 59.1%; p=0.030) compared to those who did not. However, EM RFS was similar between patients with and without acute GVHD (76.7% vs. 78.2%; p=0.744). Among the 65 patients who relapsed, 32 patients attained complete remission with salvage treatments and 22 experienced a second relapse, which occurred in the BM (n=9), BM and EM sites (n=1), or EM sites (n=12).

Our study confirms that GVHD after allogeneic hematopoietic cell transplantation has an anti-leukemic effect, thus preventing relapse; however, it may be less effective in preventing EM relapse.