Isolated Extramedullary Relapses after Allogeneic Hematopoietic Stem Cell Transplantation for Acute Leukaemia: Single-Center Experience with 220 Patients.

Extramedullary (EM) relapses of acute leukaemia (AL) without concomitant bone marrow (BM) involvement are rare after allogeneic hematopoietic stem cell transplantation (alloHSCT) and little is known about their incidence in larger series of patients (pts) and long-term outcome. We retrospectively analysed this mode of leukemia recurrence in a cohort of 220 consecutive pts with AL (88 with ALL, 132 with AML) who underwent alloHSCT in our institution between June 1993 and May 2005. 5 out of 48 pts who relapsed (4 B-line ALL, 1 45 X, -Y, t,(8;21) AML, F/M 4/1, median age 29 years, range 28–38 years) developed isolated EM infiltrates after a median time of 13 months (range, 8–23 months) post alloHSCT. There was no evidence of leukaemic BM involvement at relapse in 5/5 pts. We revealed complete donor chimerism in 4/4 studied pts. The leukaemic origin of pathologic massess was confirmed in each case by immunohistochemical methods or flow cytometry with the use of appropriate combination of the following markers: CD10, CD19, CD20, CD45, CD79a, CD34, TdT, MPO. Our data indicate that isolated EM disease following alloBMT affects predominantly high-risk ALL pts. Sites of EM relapses varies widely among the pts, however, in most of them are localised outside the well-defined sanctuaries (i.e. CNS or testis). Local radiation therapy seems to be the most effective treatment option, however, the long-term ouctomes of the pts with EM tumors remain poor. According to our experience in selected pts individualized menagement, such as intraarterially administered anthracyclines or “total skin irradiation” may be of value. Characteristics and clinical course of pts with isolated EM relapse post alloHSCT are summarized in the table below.