Results from a recent retrospective study demonstrate that the risk of infection is significantly higher in multiple myeloma patients compared to the general population.

Furthermore, the study investigators found that the rate of infection in myeloma patients has increased in recent years.

“Our study raises the question whether modern myeloma therapy increases the risk of infections,” said Dr. Cecilie Blimark from the Sahlgrenska University Hospital in Gothenburg, Sweden, who presented the study findings at the American Society of Hematology (ASH) annual meeting last month.

“The increasing risk [of developing an infection] in later years [of the study period] calls for more studies concerning new strategies regarding infectious complications and its prevention,” she concluded.

Dr. Blimark pointed out that myeloma patients are particularly prone to developing infections due to their weakened immune system. “The unique immune deficiency of myeloma patients is caused not only by treatment but by the disease itself,” she said.

According to Dr. Blimark, the risk of infection in multiple myeloma patients has not previously been directly compared to that of the general population.

Dr. Blimark and her colleagues therefore compared the risk of infections in myeloma patients and the general population in Sweden.

The study was based on data from 9,253 multiple myeloma patients diagnosed between 1988 and 2004 and 34,931 matched individuals from the general Swedish population. The median age was 72 years in both groups.

For each myeloma patient in the study, approximately four comparable individuals from the general population were chosen based on age, gender, and geographic location (county).

Overall, the study found that myeloma patients were found to be 7.1 times more likely to develop a bacterial or viral infection than the general population.  The risk was especially high during the first year after diagnosis: myeloma patients were 11.6 times more likely to develop an infection during this time compared to the general population.

More specifically, the risk of developing a bacterial infection was 7.1 times higher in myeloma patients than in the general population. Myeloma patients were especially susceptible to septicemia (blood poisoning), meningitis, and pneumonia.

This risk of developing a viral infection – such as viral flu or shingles – was 10 times higher for myeloma patients compared to the general population.

About 10 percent of the myeloma patients in the study died within two months of their diagnosis, and about 20 percent of those who died in that period died as a result of an infection.

Infection also accounted for about 20 percent of the deaths among myeloma patients who died within a year of diagnosis.  About one quarter of the myeloma patients in the study died within that time period after diagnosis.

Another key finding by Dr. Blimark and her colleagues was that the risk of infection among multiple myeloma patients increased over time.

Between 1988 and 1993, myeloma patients were 5.7 times more likely to develop an infection than the general population. This risk increased to 7.0 between 1994 and 1999, and 8.9 between 2000 and 2004.

The Swedish study was not designed to determine what may have caused the increase over time in the risk of infection.  However, the study results raise the possibility that changes over the past 25 years in the way myeloma is treated may be responsible for the increased risk of infection experienced by myeloma patients.

For more information, please see abstract 945 ^[1] at the ASH meeting website.