CRITERIA FOR EVALUATING DISEASE RESPONSE AND PROGRESSION IN PATIENTS WITH MULTIPLE MYELOMA TREATED BY HIGH‐DOSE THERAPY AND HAEMOPOIETIC STEM CELL TRANSPLANTATION

Multiple myeloma (MM) is a malignant plasma cell disorder accounting for about 10% of haematological malignancies. The disease is characterized by the clonal proliferation of plasma cells which produce a monoclonal immunoglobulin heavy and/or light chain (paraprotein, M-protein or Mcomponent). This patient-specific paraprotein is present in the serum and/or urine of all patients except in the 1–2% of patients with non-secretory myeloma. Typical clinical and laboratory features in patients with MM include bone pain (due to lytic lesions or osteoporosis), anaemia, renal insufficiency, hypercalcaemia, increased susceptibility to infection and constitutional symptoms resulting in poor performance status. Less common complications include cord compression due to extramedullary plasmacytomas or vertebral collapse, peripheral neuropathy, amyloidosis and hyperviscosity syndrome (Malpas, 1998). Prior to the introduction of alkylating agents, the median survival of patients with MM was less than a year (Korst et al, 1964; Holland et al, 1966). Approximately 60% of patients respond to initial treatment with conventional chemotherapy, but although survival is prolonged by treatment the median survival remains approximately 3 years (Bergsagel, 1998). Complete remissions are rare and all patients ultimately relapse, resulting in c 25% survival at 5 years and <10% survival at 10 years. Criteria by which different treatment regimens can be evaluated include the proportion of patients achieving an objective response, the duration of response, and survival. Over the past 10–15 years high-dose therapy followed by haemopoietic stem-cell rescue, either allogeneic or autologous, has been increasingly employed in the treatment of multiple myeloma. For a number of reasons the existing criteria for the assessment of disease response have not proved entirely satisfactory for the analysis of disease outcome after high-dose therapy. In particular, there has been no generally agreed definition of complete response. Agreed definitions of response and progression are essential to ensure consistency of reporting within the transplant registries and to enable comparison of results from different studies and/or different treatment centres. New criteria for response and progression have therefore been developed as a result of discussions between representatives of the Myeloma Subcommittee of the Chronic Leukaemia Working Party of the European Group for Blood and Marrow Transplantation (EBMT) and representatives of the Myeloma Working Committee of the Autologous Blood and Marrow Transplant Registry (ABMTR) and the International Bone Marrow Transplant Registry (IBMTR). These criteria will now form the working definitions of response and progression for the purposes of data collection and registry-based studies. Currently none of the registries include specific diagnostic criteria, although all record the relevant investigations performed at diagnosis. However, we wish to emphasize that all patients undergoing high-dose therapy should have proven myeloma which requires treatment. At present highdose therapy is not recommended for patients with equivocal myeloma or those with stage I disease. We have not at this stage reviewed the criteria for the diagnosis of myeloma, but there may be a requirement for this in the future. For example, because of the increasing use of high-dose therapy for the treatment of primary amyloidosis, it will be important to establish clear guidelines for the differential diagnosis between this condition and multiple myeloma with amyloid.