Health impact of monoclonal gammopathy of undetermined significance (MGUS) and monoclonal B-cell lymphocytosis (MBL): findings from a UK population-based cohort

Abstract

Objective: To examine mortality and morbidity patterns before and after premalignancy diagnosis in individuals with monoclonal gammopathy of undetermined significance (MGUS) and monoclonal B-cell lymphocytosis (MBL) and compare their secondary healthcare activity to that of the general population.

Design: Population-based patient cohort, within which each patient is matched at diagnosis to 10 age-matched and sex-matched individuals from the general population. Both cohorts are linked to nationwide information on deaths, cancer registrations and Hospital Episode Statistics.

Setting: The UK's Haematological Malignancy Research Network, which has a catchment population of around 4 million served by 14 hospitals and a central diagnostic laboratory.

Participants: All patients newly diagnosed during 2009-2015 with MGUS (n=2193) or MBL (n=561) and their age and sex-matched comparators (n=27 538).

Main outcome measures: Mortality and hospital inpatient and outpatient activity in the 5 years before and 3 years after diagnosis.

Results: Individuals with MGUS experienced excess morbidity in the 5 years before diagnosis and excess mortality and morbidity in the 3 years after diagnosis. Increased rate ratios (RRs) were evident for nearly all clinical specialties, the largest, both before and after diagnosis, being for nephrology (before RR=4.29, 95% CI 3.90 to 4.71; after RR=13.8, 95% CI 12.8 to 15.0) and rheumatology (before RR=3.40, 95% CI 3.18 to 3.63; after RR=5.44, 95% CI 5.08 to 5.83). Strong effects were also evident for endocrinology, neurology, dermatology and respiratory medicine. Conversely, only marginal increases in mortality and morbidity were evident for MBL.

Conclusions: MGUS and MBL are generally considered to be relatively benign, since most individuals with monoclonal immunoglobulins never develop a B-cell malignancy or any other monoclonal protein-related organ/tissue-related disorder. Nonetheless, our findings offer strong support for the view that in some individuals, monoclonal gammopathy has the potential to cause systemic disease resulting in wide-ranging organ/tissue damage and excess mortality.

Keywords: epidemiology; leukaemia; lymphoma; myeloma; public health.

Figure 1

Inpatient (IP) and outpatient (OP) monthly hospital visit activity rates 5 years before to 3 years after diagnosis (cases)/pseudodiagnosis (controls) excluding haematology attendances. (A) Monoclonal gammopathy of undetermined significance (MGUS) and (B) monoclonal B-cell lymphocytosis (MBL) diagnosed during 2009–2015.

Figure 2

Percentage of cases and controls with at least two specialty-specific outpatient visits in the 3 years before and after diagnosis of monoclonal gammopathy of undetermined significance. Top 25 recorded specialties, with visits within 1 month of diagnosis/pseudodiagnosis excluded.

Figure 3

Monthly outpatient attendance rates (per 100 persons) in cases and controls and rate ratios by outpatient specialty with at least two visits (A) in the 3 years before diagnosis and (B) in the 3 years after diagnosis of monoclonal gammopathy of undetermined significance.