Patterns of multiple myeloma during the past 5 decades: stable incidence rates for all age groups in the population but rapidly changing age distribution in the clinic

Abstract

Objective: To define age-adjusted incidence trends in multiple myeloma (MM) in a well-characterized population during a long period, given that some, but not all, studies have reported increasing MM incidence over time and that clinical experience from some centers suggests an increased incidence mainly in younger age groups.

Patients and methods: We identified all patients (N=773) with MM diagnosed in Malmö, Sweden, from January 1, 1950, through December 31, 2005. Using census data for the population of Malmö, we calculated age- and sex-specific incidence rates. Incidence rates were also calculated for 10-year birth cohorts. Analyses for trends were performed using the Poisson regression.

Results: From 1950 through 2005, the average annual age-adjusted (European standard population) incidence rate remained stable (Poisson regression, P=.07 for men and P=.67 for women). Also, comparisons between 10-year birth cohorts (from 1870-1879 to 1970-1979) failed to detect any increase. Between 1950-1959 and 2000-2005, the median age at diagnosis of MM increased from 70 to 74 years, and the proportion of newly diagnosed patients aged 80 years or older increased from 16% to 31%.

Conclusion: Our finding of stable MM incidence rates for all age groups during the past 5 decades suggests that recent clinical observations of an increase of MM in the young may reflect an increased referral stream of younger patients with MM, which in turn might be a consequence of improved access to better MM therapies. Importantly, because of the aging population, the proportion of patients with MM aged 80 years or older doubled between 1950-1959 and 2000-2005.

FIGURE 1.

Average number of cases of multiple myeloma diagnosed per year, by age at diagnosis and calendar period (1950-1979 vs 1980-2005).

FIGURE 2.

Annual incidence rates of multiple myeloma per 100,000 population in Malmö, Sweden, 1950-2005, by age and sex (left, men; right, women).