The impact of M-component type and immunoglobulin concentration on the risk of malignant transformation in patients with monoclonal gammopathy of undetermined significance

BACKGROUND AND OBJECTIVES

In this study the impact of gender, age, type of M-component and concentration of immunoglobulins on the risk of malignant transformation in monoclonal gammopathy of undetermined significance (MGUS) was assessed.

DESIGN AND METHODS

We identified 1,247 cases of MGUS in the period 1978 to 1993 in North Jutland County, Denmark. Data on cancer occurrence in the MGUS cohort were obtained from the Danish Cancer Registry. The expected numbers of incident cancer cases were calculated from age-, sex-, county-, and period-specific cancer incidence rates. The impact of the variables mentioned above on the risk of malignant transformation was analyzed in Poisson regression models.

RESULTS

The relative risk of IgA compared to IgG was 1.8 (95% confidence interval, 1.1-3.0), while the relative risk of IgM compared to IgG was 1.1 (0.7-1.9). For all three types of MGUS, the risk of malignant transformation was higher among females than among males, and the risk increased with increasing concentration of immunoglobulin with very high risks for the patients with the highest levels of immunoglobulin. Hypogammaglobulinemia was associated with malignant transformation in patients with IgG type MGUS. For IgG and IgM MGUS, the risk decreased with increasing age and with follow-up beyond one year.

INTERPRETATION AND CONCLUSIONS

Female sex, IgA M-component type and high concentration of the immunoglobulin comprising the M-component were associated with a high risk of malignant transformation. Hypogammaglobulinemia, young age at diagnosis and short follow-up were risk factors in particular for those with IgG MGUS.

Cancer risk in patients with monoclonal gammopathy of undetermined significance

To assess the cancer risk of monoclonal gammopathy of undetermined significance (MGUS) we identified 1229 cases of MGUS in the period 1978 to 1993. Data on cancer occurrence in the MGUS cohort were obtained from the Danish Cancer Registry. The expected numbers of cancer cases were calculated from age-, sex-, county-, and period-specific cancer incidence rates. In the MGUS cohort 64 new cancers with a known association with M-components were diagnosed versus 5.0 expected giving a standardized incidence ratio (SIR) of 12.9 (95% confidence interval, 9.9-16.5). The relative risks of developing multiple myeloma (SIR 34.3), Waldenström's macroglobulinemia (SIR 63.8), and non-Hodgkin's lymphoma (SIR 5.9) were significantly increased and independent of time passed from detection of the M-component. The relative risk of chronic lymphocytic leukemia was not significantly increased, SIR 2.7 (0.5-7. 7). Among cancer sites without known association with M-components 141 cases were observed versus 94.6 expected giving a SIR of 1.5 (1. 3-1.8). This enhanced risk was seen for several non-hematological cancer sites but for most cancer sites the risk was dependent on time passed from detection of the M-component, indicating a bias rather than a causal role of MGUS.

The risk of bacteremia in patients with monoclonal gammopathy of undetermined significance

We estimated the risk of bacteremia in patients with monoclonal gammopathy of undetermined significance (MGUS) compared with the general population; 1237 cases of MGUS were identified by linking information on detected monoclonal components in the North Jutland County with the Danish Cancer Registry. We evaluated the risk of bacteremia in the MGUS cohort during the 13-yr period from 1981 to 1993 by linkage to the Bacteremia Registry in the County. Follow-up for the occurrence of bacteremia started 30 d after detection of the M-component and continued until malignant transformation, death or until 31 December 1993, whichever came first. The expected numbers of bacteremia was based upon county, age, sex and period-specific incidence rates. The median follow-up period was 3.8 yr. Forty episodes of bacteremia occurred during 5500 person-years versus 18 expected. The crude standardized incidence ratio of bacteremia was 2.2 (95% confidence interval, 1.6-3.0). There was no distinct pattern of bacterial etiology in the MGUS cohort. Although we found an association between MGUS and risk of bacteremia, the overall risk is small and this finding hardly affects the clinical handling of MGUS patients.

[Renal insufficiency in myelomatosis. Prognostic factors and survival]

Clinical features, occurrence and reversibility of renal failure, response to treatment and survival duration in 190 multiple myeloma patients were reviewed in a retrospective study based on hospital records. Renal failure was present in 27% of the patients and constituted an important prognostic factor. Reversibility of renal failure occurred in 52% of the patients and was more frequent in those with low serum creatinine, hypercalcaemia, high erythrocyte sedimentation rate and high level of IgA. Response to chemotherapy resulted in a prolonged survival, whereas recovery of renal function did not significantly affect survival.

[Occult hereditary spherocytosis in aplastic crisis of unknown cause]

We describe two cases of aplastic crisis of unknown origin, occurring within one week in a 49-year old man and his 20 year old son. They both had undiagnosed hereditary spherocytosis, and both of them had earlier had a B19-parvo infection without having symptoms of aplastic crisis at the same time. Chronic haemolytic anaemia should be considered in adult patients with acute severe anaemia caused by aplastic crisis.