Survival of cancer patients with prior monoclonal gammopathy of undetermined significance

INTRODUCTION: It is unknown whether a prior diagnosis of monoclonal gammopathy of undetermined significance (MGUS) affects cancer survival. DESIGN AND METHODS: We linked data on 1652 cases of MGUS diagnosed during 1978-2006 in North Jutland County, Denmark with the Danish Cancer Registry and the National Patient Registry to obtain information on survival of cancer patients with a previous MGUS compared with that of cancer patients without MGUS, matched on cancer type, age, sex and year of diagnosis. Stratified Cox regression analysis was used to compute mortality rate ratios controlling for the matching factors and comorbidity. RESULTS: We included 323 cancer patients with previously detected MGUS and 3154 comparison cancer patients without MGUS. The 5-year survival probability was 26.2% (95% CI, 21.2%-31.5%) in cancer patients with MGUS and 30.5% (28.8%-32.1%) in cancer patients without MGUS. The adjusted mortality rate ratio (MRR) was=0.94 (95% CI, 0.82-1.09). Survival following a diagnosis of multiple myeloma, the cancer site of main interest, did not differ according to a preceding MGUS diagnosis. Among patients with immune-related cancers (liver, cervix, malignant melanoma and non-melanoma skin cancers), a preceding MGUS diagnosis was associated with reduced survival (adjusted MRR=1.49 (95% CI: 0.96-2.31)). In contrast, for other non-haematological cancers a prior MGUS diagnosis was associated with a lower MRR (0.78 (95% CI, 0.63-0.96)). CONCLUSION: Our study does not indicate that previously detected MGUS is a prognostic factor for cancer survival in general.