The staging of the tumour. There is a group of patients who are suspected as having early or incipient myeloma with a low serum concentration of monoclonal immunoglobulin (the paraprotein), whose bone marrow contains less than 10% of plasma cells and whose skeletal survey shows no bone lesions; such patients do not qualify for the diagnosis of myeloma but are referred to as ‘monoclonal gammopathy of uncertain significance’ (or MGUS).
These patients and those with bone marrow infiltration of 10-30% of plasma cells (also called ‘smouldering myeloma’), as well as all the ‘solitary plasmacytoma’ patients must be kept under careful observation as multiple myeloma may well develop in the future in all these categories.
In patients who ‘qualify’ as suffering multiple myeloma, the prognosis depends on several other factors: patients who present with anaemia, kidney failure, a bone marrow with a very high infiltrate of plasma cells (or worse a plasma cell leukaemia on the peripheral blood film), and those with a very high serum paraprotein level all have a worse outlook for survival than those who do not demonstrate these characteristics on presentation.
In more research settings, the measurement of labelling indices (a measure of the fraction of a malignant clone of cells in the throws of division at any one time) and the urinary levels of a protein called B2-microglobulin both add to useful prognostic assessment of patients.
