Multiple myeloma patients with fewer circulating plasma cells appear to survive longer than patients with more circulating plasma cells, according to a study published in the journal Blood. These findings may influence treatment since patients with higher levels of plasma cells may benefit from more aggressive therapy than those with fewer circulating plasma cells.
Multiple myeloma is a plasma cell cancer. Plasma cells, an important part of the immune system, produce antibodies to help fight infection and disease. In multiple myeloma, abnormal plasma cells form tumors in bone marrow, which can prevent the bone marrow from producing healthy blood cells. Although multiple myeloma is not curable, it can be treated so that patients may live longer, healthier lives.
Because survival can vary greatly among patients with multiple myeloma (from a median of 3-4 years to 7-10 years or longer), there is interest in identifying factors that influence survival. Researchers at the Mayo Clinic hypothesized that a higher number of plasma cells in circulating blood (in other words, outside of the bone marrow) could indicate more aggressive multiple myeloma with shorter expected survival. Previous studies provide support for this idea, but used a labor-intensive laboratory method that is not practical for widespread testing. In search of a solution, Mayo Clinic investigators conducted a study to determine whether the number of circulating plasma cells as identified by flow cytometry, a quick and readily available laboratory test, is associated with multiple myeloma survival.
The study involved 203 patients with newly diagnosed multiple myeloma. Counts of circulating plasma cells were obtained by flow cytometry and expressed as the number of plasma cells per 50,000 cells evaluated. Twenty-seven percent of patients had no circulating plasma cells, 35% had one to 10 circulating plasma cells, and 38% had more than 10 circulating plasma cells. Survival was longer among the patients with fewer circulating plasma cells:
- Among patients with 10 or fewer circulating plasma cells, half survived for at least 59 months.
- Patients with more than 10 circulating plasma cells survived only up to 37 months.
The researchers conclude that the number of plasma cells in circulating blood, as measured by flow cytometry, predicts multiple myeloma survival. Longer survival is predicted among patients with fewer circulating plasma cells. Given the availability of flow cytometry at most medical centers, the researchers suggest that future clinical trials of multiple myeloma therapies should include assessment of circulating plasma cells as part of the pretreatment exam. Patients with multiple myeloma may wish to talk with their doctor about the risks and benefits of participating in a clinical trial evaluating therapeutic approaches.
Reference: Nowakowski GS, Witzig TE, Dingli D et al. Circulating plasma cells detected by flow cytometry as a predictor of survival in 302 patients with newly diagnosed multiple myeloma. Blood. 2005;106:2276-2279.