Multiple myeloma is a plasma cell neoplasm characterized by skeletal destruction, renal failure, anemia, and hypercalcemia. The disease is incurable. Myeloma develops with the emergence of clonal plasma cells, clinically known as monoclonal gammopathy of undetermined significance (MGUS). At this stage, patients do not show signs of end-organ damage; however, there is a 1% annual risk of progression to myeloma or a related malignant disease. As the disease progresses, complex genetic events occur in the bone marrow microenvironment. The interactions of myeloma cells, bone marrow cells, and microvessels lead to a progression of the tumor and a resistance to drugs. The development of bone lesions is a result of changes in bone turnover.¹

Multiple myeloma is the second most prevalent blood cancer after non-Hodgkin's lymphoma. It represents approximately 1% of all cancers and 2% of all cancer deaths.^2,3

The median age at diagnosis is about 71 years; only 2% of cases are diagnosed in individuals younger than age 45. An estimated 50,000 Americans currently have myeloma. According to the American Cancer Society, approximately 15,270 new cases of myeloma will be diagnosed during 2004.^2,3

Multiple myeloma affects slightly more men than women (of the estimated 15,270 new cases referenced above, 8090 are expected to occur in men versus 7180 in women). African Americans and Native Pacific Islanders have the highest reported incidence of this disease, and Asians, the lowest. A recent study found the incidence of myeloma to be 9.5 cases per 100,000 African Americans and 4.1 cases per 100,000 Caucasian Americans. Among African Americans, myeloma is one of the leading causes of cancer death.^2,3

Little is known about the etiology of multiple myeloma. However, there are some factors that appear to make a person more likely to develop multiple myeloma. These factors are discussed below.⁴

• Increasing age is the most significant risk factor. According to the American Cancer Society, people younger than 40 years make up only 2% of multiple myeloma cases. The average age of a patient at diagnosis is about 70.
• African Americans are diagnosed with multiple myeloma about twice as often as Caucasian Americans.
• People who are exposed to herbicides, insecticides, petroleum products, heavy metals, plastics, and asbestos have a higher-than-average chance of developing multiple myeloma.
• People who have other medical conditions that affect the plasma cells are at increased risk of developing multiple myeloma. These conditions include isolated plasmacytoma of bone, MGUS, and extramedullary plasmacytoma.
• Exposure to high doses of radiation may be a risk factor, but according to the American Cancer Society, it accounts for a very small number of cases.
• Family history of multiple myeloma may put a person at somewhat greater risk; however, most multiple myeloma patients do not have relatives with the disease.
• Researchers recently have discovered that many myeloma patients have Kaposi's sarcoma-associated herpes virus in their blood. The possibility that this virus is associated with myeloma is being investigated.

Because the majority of diagnoses occurs among older adults, it is thought that susceptibility to the disease may increase with the aging process and the consequent reduction in immune surveillance of evolving cancer. Another hypothesis is that myeloma may result from a lifelong accumulation of toxic insults or antigenic challenges.²

1.	Kyle RA. Drug therapy: multiple myeloma. NEJM. 2004;351:1860-1873.
2.	Berenson JR, San Miguel J. Causes and incidence. Multiple Myeloma Research Foundation. Available at http://www.multiplemyeloma.org/about_myeloma/2.03.html. Accessed December 2004.
3.	Jemal A, Tiwari RC, Murray T, et al. Cancer Statistics, 2004. CA Cancer J Clin. 2004;54:8-29.
4.	Multiple myeloma disease basics. HealthTalk. Available at http://www.healthtalk.com/multiplemyeloma/diseasebasics.cfm. Accessed December 2004.