Prepared by staff in Prevention and Cancer Control. Multiple myeloma – age at diagnosis and trends over time (Nov. 2012) The pattern of age at diagnosis for multiple myeloma is different from other cancers that affect blood cells and bone marrow. Incidence rates are stable in males and declining in females. The causes of multiple myeloma remain poorly understood. Multiple myeloma is one type of several cancers that begin in blood cells and bone marrow, but has a rather different pattern of age at diagnosis than those other cancers, the lymphomas and leukemias. Multiple myeloma cases are rarely diagnosed before age 40. In fact, less than 1% of multiple myeloma cases are diagnosed under age 40 compared to approximately 8% for non-Hodgkin lymphoma, 12% for leukemia and 36% for Hodgkin lymphoma. The median age at diagnosis for multiple myeloma is 71, slightly older than for leukemia, non-Hodgkin lymphoma or Hodgkin lymphoma at ages 68, 66 and 36, respectively. In Ontario, 868 new cases of multiple myeloma were diagnosed in 2009, 492 (57%) of which were in males. Incidence rates in males remained stable between 1981 and 2009, although there is some suggestion of a non- significant decline since 2003. Meanwhile, incidence rates in females increased significantly between 1981 and 2001 at 0.7% per year, and then decreased significantly at 2.4% per year from 2001 until 2009. The reasons for the recent decline are unclear. The causes of multiple myeloma are poorly understood, but researchers know that its development involves a complex multi-step process. It starts when malignant plasma cells begin accumulating in the bone marrow, which eventually results in bone lesions and impaired immune functioning. A majority of multiple myeloma cases evolve from a pre-malignant condition called monoclonal gammopathy of undetermined significance (MGUS).1 Only about 1% of MGUS cases, however, go on to develop into full-blown multiple myeloma and there is no reliable way to predict whether this more serious disease progression will occur.2 Genetic risk factors may play a role because studies have shown that multiple myeloma and MGUS tend to cluster in families, and the risk of developing this condition is higher among people with an affected sibling or parent.3 In addition, studies from the United States show that African Americans are nearly twice as likely as Caucasians to be diagnosed with multiple myeloma.2 Chronic immune stimulation (infections or chronic inflammation, for example) and autoimmune disorders have been investigated as possible risk factors for multiple myeloma because this disease affects the immune system; the findings of these studies have been somewhat contradictory. Higher rates of multiple myeloma among agricultural workers brought attention to pesticides as a potential risk, but the results of these studies have also been inconsistent. Although early research on atomic bomb survivors in Japan reported an excess risk of multiple myeloma in this population,2 recent studies of workers in the nuclear industry, medical radiation workers, and people with occupational or residential exposure to extremely low frequency electromagnetic fields do not indicate that radiation causes multiple myeloma.2 More research is needed so that we can gain a more complete understanding of what triggers this type of cancer. References Raab MS, Podar K, Breitkreutz I, et al. Multiple myeloma. Lancet 2009;374:324–39. Alexander DD, Mink PJ, Adami HO, et al. Multiple myeloma: a review of the epidemiologic literature. Int J Cancer 2007;120 Suppl 12:40–61. Greenberg AJ, Rajkumar SV, Vachon CM. Familial monoclonal gammopathy of undetermined significance and multiple myeloma: epidemiology, risk factors, and biological characteristics. Blood 2012;119:5359–66. Citation: Cancer Care Ontario. Cancer Fact: Multiple myeloma – age at diagnosis and trends over time. November 2012. Available at http://www.cancercare.on.ca/cancerfacts. Prepared by staff in Prevention and Cancer Control.