Isolated extramedullary relapse of acute lymphoblastic leukaemia after allogeneic bone marrow transplantation

Isolated extramedullary relapse of acute lymphoblastic leukaemia (ALL) with sparing of the marrow after allogeneic bone marrow transplantation (BMT) is a rare occurrence, and the mechanisms underlying the selective involvement of extramedullary sites remain undefined. These might be due to relapse in sanctuary sites where the leukaemic cells are resistant to chemotherapy, or a stronger putative graft-versus-leukaemia (GVL) effect in the marrow as compared with peripheral tissues. We report two ALL patients with repeated episodes of extramedullary relapse after BMT in whom both mechanisms might be operating. In the first patient, the marrow was in morphologic and molecular remission before isolated leukaemic relapse in the central nervous system (CNS) occurred. Subsequent secondary infiltration of leukaemic cells into the marrow was only evident molecularly but not morphologically, implying that the relapse had arisen in a sanctuary CNS site. In the second patient, a first relapse in the marrow, which was induced into morphologic and molecular remission by chemotherapy and donor lymphocyte infusion, was followed by extramedullary relapses without any subsequent involvement of the marrow. This suggested that factors, likely to be due to a GVL effect, were stronger in the marrow than in peripheral tissues.     

Biological importance of residual leukaemic cells after BMT for CML: does the polymerase chain reaction help?

The fate of the leukaemic clone after bone marrow transplantation (BMT) for patients with chronic myeloid leukaemia (CML) may determine the long-term prognosis. Several groups have reported the use of the polymerase chain reaction (PCR), a highly sensitive technique for detecting residual leukaemia, to study blood and bone marrow of patients in apparent cytogenetic and clinical remission at various intervals after BMT. The limitations of the technique relate to the need in CML to use mRNA rather than DNA as test material, the undefined sensitivity of the assay, the lack of knowledge of cell lineage when the test is positive and the high risk with present techniques of false positive and false negative findings. These points notwithstanding, the collected data suggest that most longterm survivors have no evidence of leukaemia detectable by PCR; in contrast many of the patients transplanted within the last 5 years do have evidence of residual leukaemia. This suggests that in a significant number of patients the leukaemic clone may survive for several years after BMT before it is eradicated (or falls below the threshold for detection by PCR). If this is confirmed the finding of residual leukaemia by PCR in the first few years post-BMT would have limited prognostic significance.     

Minimal residual disease after allogeneic bone marrow transplantation for chronic myeloid leukaemia: a metaphase-FISH study

Metaphase-FISH was adopted for the detection of proliferating Philadelphia-positive (Ph⁺) residual leukaemic cells in 25 patients with chronic myeloid leukaemia treated with allogeneic bone marrow transplantation (BMT). Patients were followed up during their clinical remission for 4–50 months (median 17 months) after BMT. 80 bone marrow samples were studied. For most of the cases no fewer than 1000 metaphases were analysed. Six patients (24%) showed residual Ph⁺ cells during the first 6 months and two others by the end of the first year after BMT. Three patients relapsed during the study and in two of them residual Ph⁺ cells were detected during the first 6 months after BMT. In 17 patients no Ph⁺ cells were detected at any stage of follow-up and 16 (94.1%) of them continue in complete clinical and haematological remission. Our results indicate that metaphase-FISH is a reliable tool in the quantitation of proliferating residual leukaemic cells. We suggest that consecutive findings of equal amounts of residual leukaemic cells do not necessarily predict a relapse. However, their presence calls for follow-up at shorter intervals where an increasing number of these cells predicts an ensuing relapse.     

Relapse after allogeneic bone marrow transplantation for acute leukaemia: a survey by the E.B.M.T. of 117 cases

A multi-centre retrospective analysis on 117 patients relapsing after bone marrow transplantation (BMT) for acute leukaemia was carried out by the Leukaemia Working Party of the European Group for Bone Marrow Transplantation (E.B.M.T.). Forty-one patients had acute myeloid leukaemia (AML) and 76 had acute lymphoblastic leukaemia (ALL). Relapse occurred between 3 and 30 months after BMT and where investigated the leukaemia was found to have relapsed in recipient cells. In 10 cases the relapse was associated with new cytogenetic abnormalities. 74 patients received further treatment for leukaemia. Of these 21 out of 50 with ALL and 11 out of 24 with AML achieved a complete remission and had a median survival of 12 months compared with a median survival of 4 months for untreated patients or patients not achieving complete remission (P less than 0.001). Factors predictive for successful remission induction were a long interval between bone marrow transplant and relapse in ALL patients; and isolated extramedullary relapse. Presenting blast count, karyotype and remission status and number at the time of BMT were not predictive. Donor bone marrow was shown to be responsible for haemopoietic recovery occurring in the 21 out of 31 patients tested who achieved remission using donor karyotype or red blood cell antigens as markers. Nine patients received a second bone marrow transplant but only one became a long-term survivor. The results show that chemotherapy can usually prolong survival in selected patients with acute leukaemia relapsing after BMT but further BMT has a poor outlook.