Chapter 4: Cancer incidence in Canada: trends and projections (1983-2032) – Multiple myeloma - HPCDP: Volume 35, Supplement 1, Spring 2015

Chapter 4: Projections by Cancer Site

22. Multiple myeloma

Multiple myeloma (MM), or plasma cell myeloma, is the third most common lymphohematopoietic cancer, after NHL and leukemia. During 2003–2007, the average annual number of newly diagnosed MM cases was 1065 for males and 875 for females in Canada, which represented 1.3% and 1.2% of all new male and female cancer cases, respectively (Tables 4.22.1 and 4.22.2).

The estimated lifetime risk of developing MM is 1 in 131 for males and 1 in 157 for females.^{Endnote 1} Incidence was rare below age 45, accounting for 2.8% and 2.3% of the respective male and female cases in 2003–2007, while nearly 56% to 58% of the cases were diagnosed in people aged 65 to 84 (Tables 4.22.1 and 4.22.2). The incidence rates increased gradually with age (Tables 4.22.3 and 4.22.4). The overall male-to-female ratio was 1.5. MM has a poor prognosis among all lymphohematopoietic cancers, with a 5-year survival rate of 43% in 2006–2008.^{Endnote 1}

The overall incidence rates of MM have increased marginally throughout the whole observation period in males (Figure 4.22.1). The similar magnitude of the increase in females showed levelling off in the last 10 years. During 1998–2007, the ASIRs for MM increased non-significantly in males by 0.4% per year and were stable in females (Figures 3.1 and 3.2). Rate stabilization has been observed in all regions, the only variation being a decrease in British Columbia in the last period. The interregional differences in ASIRs were small, ranged from 5.0 to 6.7 per 100 000 in males and 3.0 to 4.5 in females.

The incidence rates of MM in males are expected to increase by 3% to 13% in all regions from 2003–2007 to 2028–2032 (Figure 4.22.1). When the Atlantic region is not considered, the observed east–west gradient in male rates that started in 1998– 2002 will remain over the next 25 years, with the highest rates in Quebec and the lowest rates in British Columbia. The rates in females are projected to stabilize in the Atlantic region and Ontario and increase marginally (4%–8%) in the other regions. Females in Ontario are predicted to experience the highest incidence, whereas those in British Columbia will have the lowest rates. The age-specific analysis illustrated in Figure 4.22.2 indicates that the ASIRs in Canada are expected to increase slightly or stabilize in each age group, resulting from continuation of their observed long-term trends.

From 2003–2007 to 2028–2032, the ASIRs of MM for the country are projected to increase by 11% in males, from 6.1 to 6.8 per 100 000, and by 4% in females, from 4.0 to 4.2 per 100 000 (Tables 4.22.3 and 4.22.4). The annual number of new male cases is projected to increase by 125%, from 1065 to 2395, and the number of new female cases is projected to increase by 92%, from 875 to 1685 (Tables 4.22.1 and 4.22.2).

Comments

In accordance with recent reports from Sweden, England and US,^{Endnote 284, Endnote 285, Endnote 286} the overall incidence rates for MM increased marginally throughout the whole observation period in Canada. The apparent increasing trends of MM in Canada and worldwide may be due to improved diagnostic practices and better case ascertainment. The role of risk factors responsible for the trends in the disease frequency should also not be ruled out.

Other than older age, male gender, Black ethnicity, family history of lymphohematopoietic cancer, and monoclonal gammopathy of undetermined significance (MGUS), there are few known risk factors for the clinical entity.^{Endnote 287} However, several factors have been implicated as potentially etiologic, although findings are inconsistent.

Numerous studies have reported increased risk of developing MM in people with a family history of cancer, specifically lymphohematopoietic cancer, although the underlying mechanisms remain elusive and family history may be responsible for a relatively small proportion of new cases.^{Endnote 287, Endnote 289} MGUS, a condition of excessive plasma cell growth, has consistently been observed to progress to MM.^{Endnote 287} Annual risk of progression from MGUS to MM is about 1%.^{Endnote 289}

Obesity has been associated consistently with an elevated risk of MM. Researchers at the Karolinsksa Institute, Stockholm, conducted a meta-analysis of 11 cohort studies and 4 case–control studies published from 1994 to May 2007.^{Endnote 290} In the cohort studies, overweight and obese people have a 12% and 27% increase in risk of MM, respectively. For case-control studies, the summary estimates were significantly higher. This effect was independent of age, sex and ethnicity. Their recent systematic review of 15 cohort studies is in line with these findings.^{Endnote 291}

Chronic immune stimulation conditions or autoimmune disorders have not been consistently related to MM; however, the incidence of MM appears to be elevated in people with AIDS.Endnote 287 A meta-analysis published in 2008 found that MM was 2.6 times more prevalent in HIV-infected people than the general population.Endnote 292