Monoclonal gammopathy of undetermined significance in atomic bomb survivors: incidence and transformation to multiple myeloma

Screening for M-proteinemia consisting of monoclonal gammopathy of undetermined significance and multiple myeloma for 30 years among atomic bomb survivors in Hiroshima

Monoclonal gammopathy (M-proteinemia) is a premalignant plasma cell disorder. The prevalence of M-proteinemia increases with age and is affected by genetic or environmental factors. Atomic bomb (A-bomb) survivors in Hiroshima are in an age range when they are susceptible to M-proteinemia. The prevalence and incidence of M-proteinemia in Hiroshima A-bomb survivors were investigated for 30 years (1989-2018) to examine the influence of radiation exposure. The overall prevalence of M-proteinemia among 38,602 A-bomb survivors was 2.4%. M-proteinemia prevalence at age 70 years and monoclonal gammopathy of undetermined significance (MGUS) incidence were not associated with radiation exposure category. Males had a 2.30-fold higher prevalence and a 2.08-fold higher incidence than females. The risk of incidence for MGUS was 4.32-fold higher in persons aged < 10 years at the time of the A-bombing and 2.56-fold higher in those aged 10-19 years compared with those aged over 30 years. IgG type M-proteinemia was common and the IgM type developed 5-8 years later than other immunoglobulin types. Exposure to radiation was not clearly associated with the prevalence of M-proteinemia or incidence of MGUS in Hiroshima A-bomb survivors. However, males and those aged < 20 years at A-bombing had higher susceptibility to MGUS.

Five-Year Follow-up Study of Monoclonal Gammopathy of Undetermined Significance in a Korean Elderly Urban Cohort

Purpose

We previously reported the prevalence of monoclonal gammopathy of undetermined significance (MGUS) to be 3.3% among an elderly Korean urban cohort recruited during 2005-2006. Here, we report a 5-year follow-up study of the previously identified MGUS cohort.

Materials and Methods

The 680 participants from the initial cohort were followed-up for a median of 5 years. Sera were collected between 2010 and 2011. Two-step screening was performed with standard serum electrophoresis followed by immunofixation and determination of the serum concentration of monoclonal-protein (M-protein).

Results

Of the 680 participants (21 with MGUS), 348 (51%) agreed to participate in the follow-up study and 10 were found to have MGUS. Among the 21 MGUS patients initially identified, nine were followed-up, six had persistent M-protein, and one patient had progressed to multiple myeloma (progression rate, 1.0%/yr). The M-protein disappeared in the remaining two individuals. Among the 339 participants without MGUS who were followed-up, four developed an M-protein. There was no significant difference in survival with respect to the presence of MGUS (p=0.66).

Conclusion

The 5-year follow-up data show that the natural clinical course of MGUS in Korea is similar to that in Western countries. MGUS was not associated with an increased risk of death over the 5-year study period.

Prevalence of monoclonal gammopathy of undetermined significance: a systematic review

Monoclonal gammopathy of undetermined significance (MGUS) is a premalignant plasma cell disorder that is associated with a lifelong risk of multiple myeloma. We conducted a systematic review of all studies investigating the prevalence and incidence of MGUS in the online database PubMed. The review was conducted from January 6, 2009, through January 15, 2010. The following MeSH search headings were used: monoclonal gammopathy, benign and prevalence; monoclonal gammopathy, benign and incidence; paraproteinemia and prevalence; and paraproteinemia and incidence. Articles were limited to those written in English and published by January 2009. Fourteen studies that met prespecified criteria were included and systematically assessed to identify the most accurate prevalence estimates of MGUS based on age, sex, and race. On the basis of our systematic review, we estimate that the crude prevalence of MGUS in those older than 50 years is 3.2% in a predominantly white population. Studies in white and Japanese populations demonstrate a clear increase in prevalence with age. The prevalence is also affected by sex: 3.7% and 2.9% in white men and women, respectively; and 2.8% and 1.6% in Japanese men and women, respectively. Additionally, MGUS is significantly more prevalent in black people (5.9%-8.4%) than in white people (3.0%-3.6%). We conclude that MGUS is a common premalignant plasma cell disorder in the general population of those older than 50 years. The prevalence increases with age and is affected by race, sex, family history, immunosuppression, and pesticide exposure. These results are important for counseling, clinical care, and the design of clinical studies in high-risk populations.

Relationship between monoclonal gammopathy of undetermined significance and radiation exposure in Nagasaki atomic bomb survivors

Radiation exposure is a possible predisposing factor for monoclonal gammopathy of undetermined significance (MGUS), but the association has been uncertain. We investigated the relationship between radiation exposure and MGUS prevalence by using data from the M-protein screening for Nagasaki atomic bomb survivors between 1988 and 2004. Radiation exposure was assessed by exposure distance from the hypocenter and exposure radiation dose. We computed prevalence ratios (PRs) and the 95% confidence intervals (CIs) adjusting for exposure age and sex. A total of 1082 cases of MGUS were identified from 52 525 participants. MGUS prevalence was significantly higher in people exposed at distance within 1.5 km than beyond 3.0 km (PR, 1.4; 95% CI, 1.1-1.9) among those exposed at age 20 years or younger, but it was not found among those exposed at age 20 years or older. MGUS prevalence was also significantly higher in people exposed to more than 0.1 Gy than those exposed to less than 0.01 Gy (PR, 1.7; 95% CI, 1.0-2.8) among those exposed at age 20 years or younger. Thus, people exposed at younger age exhibited a significantly high risk of MGUS when exposed to a high radiation dose. There was no clear association between radiation exposure and the malignant progression of MGUS. Further detailed analysis is needed.

Multiple myeloma: A review of the epidemiologic literature

Multiple myeloma, a neoplasm of plasma cells, accounts for approximately approximately 15% of lymphatohematopoietic cancers (LHC) and 2% of all cancers in the US. Incidence rates increase with age, particularly after age 40, and are higher in men, particularly African American men. The etiology is unknown with no established lifestyle, occupational or environmental risk factors. Although several factors have been implicated as potentially etiologic, findings are inconsistent. We reviewed epidemiologic studies that evaluated lifestyle, dietary, occupational and environmental factors; immune function, family history and genetic factors; and the hypothesized precursor, monoclonal gammopathies of undetermined significance (MGUS). Because multiple myeloma is an uncommon disease, etiologic assessments can be difficult because of small numbers of cases in occupational cohort studies, and few subjects reporting exposure to specific agents in case-control studies. Elevated risks have been reported consistently among persons with a positive family history of LHC. A few studies have reported a relationship between obesity and multiple myeloma, and this may be a promising area of research. Factors underlying higher incidence rates of multiple myeloma in African Americans are not understood. The progression from MGUS to multiple myeloma has been reported in several studies; however, there are no established risk factors for MGUS. To improve our understanding of the causes of multiple myeloma, future research efforts should seek the causes of MGUS. More research is also needed on the genetic factors of multiple myeloma, given the strong familial clustering of the disease.

Gene-expression signature of benign monoclonal gammopathy evident in multiple myeloma is linked to good prognosis

Monoclonal gammopathy of undetermined significance (MGUS) can progress to multiple myeloma (MM). Although these diseases share many of the same genetic features, it is still unclear whether global gene-expression profiling might identify prior genomic signatures that distinguish them. Through significance analysis of microarrays, 52 genes involved in important pathways related to cancer were differentially expressed in the plasma cells of healthy subjects (normal plasma-cell [NPC]; n=22) and patients with stringently defined MGUS/smoldering MM (n=24) and symptomatic MM (n=351) (P<.001). Unsupervised hierarchical clustering of 351 patients with MM, 44 with MGUS (24+20), and 16 with MM from MGUS created 2 major cluster branches, one containing 82% of the MGUS patients and the other containing 28% of the MM patients, termed MGUS-like MM (MGUS-L MM). Using the same clustering approach on an independent cohort of 214 patients with MM, 27% were found to be MGUS-L. This molecular signature, despite its association with a lower incidence of complete remission (P=.006), was associated with low-risk clinical and molecular features and superior survival (P<.01). The MGUS-L signature was also seen in plasma cells from 15 of 20 patients surviving more than 10 years after autotransplantation. These data provide insight into the molecular mechanisms of plasma-cell dyscrasias.