Monoclonal Gammopathies |
1 Department of Medicine, Division of Hematology, Karolinska University Hospital Solna and Karolinska Institutet, Stockholm, Sweden;
2 National Cancer Institute, National Institutes of Health, Bethesda, Md, USA;
3 Department of Medicine, Section of Hematology, Malmö University Hospital, Malmö, Sweden
Correspondence: Sigurdur Yngvi Kristinsson, M.D., Department of Medicine Division of Hematology, Karolinska University Hospital Solna, SE-171 76 Stockholm, Sweden. Phone: international +46.8.51770000; Fax: international +46.8.318264. E-mail:sigurdur.kristinsson{at}karolinska.se
Key words: MGUS, solid tumors, familial aggregation, susceptibility.
Monoclonal gammopathy of undetermined significance (MGUS) is one of the most common pre-malignant disorders in western countries with a prevalence of 3.2% in the Caucasian general population 50 years of age or older.1 It is characterized by the presence of a monoclonal immunoglobulin (M-protein) in individuals lacking evidence of multiple myeloma (MM) or other lymphoproliferative malignancies.2 Long-term follow-up of MGUS patients reveals an average 1% annual risk of developing a lymphoproliferative malignancy.3,4 Although the etiology of MM and MGUS is unknown, there is emerging evidence to support a role for genetic factors. For example, familial aggregation of both MM and MGUS has been observed.5 Also racial disparities in incidence patterns for MGUS and MM support a role for germline genes in the etiology of MM.6 Recently, we found first-degree relatives of MGUS patients to have an increased risk of MGUS, MM, lymphoplasmacytic lymphoma/Waldenströms macroglobulinemia, and chronic lymphocytic leukemia, supporting a role for shared common germline susceptibility genes in these disorders.5 Furthermore, in two recent studies an excess of certain solid tumors among blood relatives to MM patients was reported.7,8
To improve our understanding in this area, we have, to the best of our knowledge, conducted the first population-based study to evaluate familial aggregation patterns of 27 solid tumors and all myeloid hematologic malignancies among first-degree blood relatives of MGUS patients. Using high-quality population-based data from Sweden, we identified 4,458 MGUS patients and 17,505 controls, as well as all linkable first-degree relatives of patients (n=14,621) and controls (n=58,387) (Table 1). We used
2 models to calculate relative risks (RR) and 95% confidence intervals (CI) as measures of familial aggregation.
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Table 1. Characteristics of MGUS patients and matched controls.
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The observed increased risk for bladder cancer among relatives of MGUS patients agrees with a prior study showing evidence of co-aggregation of MM and bladder cancer.9 Furthermore, in a study based on patients with a coexisting MGUS and a solid tumor, 24% had bladder cancer.10 Also in agreement with a previous study by Camp et al.,7 we found first-degree relatives of MGUS cases to have a borderline increased risk of malignant melanoma. These findings are further supported by a prior genotyping study, suggesting that germline mutations in the CDKN2A gene may predispose to both MM and malignant melanoma.11 Our finding of a borderline increased risk of lung cancer among relatives of MGUS patients needs to be confirmed by other studies. However, one small study found family history of lung cancer to be associated with an increased risk of MM in elderly patients,12 a finding not observed in our previous Swedish MM study.6 In contrast to two prior studies focusing on solid cancers in MM families, 7,8 we did not find a significantly increased risk of prostate cancer among MGUS relatives. Based on small numbers, we found excess risk of spinal cancer among MGUS relatives. Because we evaluated a large number of malignancies, it cannot be ruled out that this finding is due to chance. Finally, we did not find an increased risk of myeloid malignancies among first-degree relatives suggesting that myeloid and lymphoid hematologic malignancies have different mechanisms with regard to etiology. Our study has several strengths, including its large size as well as the application of high-quality data. The use of the nationwide register-based case-control design ruled out recall-bias, ensured a population-based setting, and generalizability of our findings. The nature of this study is hypothesis-generating and one has to interpret our findings with caution due to the large number of tested malignancies.
Our findings support a role for a shared susceptibility (genetic, environmental, or both) that predisposes to MGUS and certain solid tumors, supporting the application of gene mapping and candidate gene approaches in high-risk families and case-control studies.
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Table 2. Relative risk of solid tumors and hematologic myeloid malignancies among first-degree relatives of MGUS patients.
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