Malignant transformation and life expectancy in monoclonal gammopathy of undetermined significance

The actuarial probability of malignant transformation and the impact on expected survival were analysed in a series of 128 persons diagnosed with monoclonal gammopathy of undetermined significance (MGUS) over a 20‐year period. At a median follow‐up of 56 months the M‐component remains stable in 101 patients (78·9%), 14 patients (10·9%) have died from non‐related disorders and 13 (10·2%) have developed malignant transformation of MGUS (multiple myeloma, 10; primary amyloidosis, two; Waldenström's macroglobulinaemia, one). The actuarial probability of malignant transformation at 5 and 10 years was 8·5% and 19·2%, respectively. When different presenting features were analysed for predictive value of the malignant transformation, the IgA type of MGUS was the only variable associated with a higher probability of such an event (P<0·025). Although no significant difference was observed between the survival probability of persons with MGUS and that of the control population, the development of malignant transformation was associated with a shorter survival (P<0·001).