September 24, 2010

Causes of Death in Anemia Patients

(Ivanhoe Newswire) -- Among patients receiving immunosuppressive therapy for severe aplastic anemia, a condition in which the bone marrow is unable to produce blood cells, the length of telomeres (chromosome markers of biological aging) was clearly associated with a higher rate of relapse and lower overall survival.

Severe aplastic anemia is characterized by life-threateningly low blood cell counts, but the condition can be treated by bone marrow transplant or immunosuppressive drugs. In older patients, or when an appropriate donor is not available, immunosuppression can be effective, although relapse can occur, as can chromosome abnormalities in bone marrow cells that accompany cancers in the blood "“ a condition referred to as clonal evolution.

Researchers have identified certain cell abnormalities as risk factors in bone marrow failure. "Mutations in telomerase complex genes resulting in extremely short telomeres have been described in some patients with apparently acquired severe aplastic anemia," the authors were quoted as saying.

The telomere, a structure at the end of a chromosome that shortens with each cell division, functions as a protective cap to prevent erosion of genomic DNA during cell division.

Phillip Scheinberg, M.D., of the National Institutes of Health, Bethesda, MD., and colleagues conducted a study to determine the effect of telomere attrition in acquired severe aplastic anemia by measuring telomere length prior to immunosuppressive therapy. The study included 183 patients with severe aplastic anemia who were treated from 2000 to 2008.

Of the patients studied, 104 responded to immunosuppressive therapy. The researchers found that there was no correlation between telomere length and the probability of response to the therapy. The response rate for patients in the first quartile (shortest telomere lengths) was 56.5 percent; in the second quartile, 54.3 percent; in the third quartile, 60 percent; and in the fourth quartile, 56.5 percent.

Additional analysis, however, demonstrated that telomere length was associated with relapse, clonal evolution, and mortality. The shorter the telomere, the greater the probability of disease relapse. The probability of clonal evolution was higher in patients in the first quartile (24.5 percent) than in quartiles 2 through 4 (8.4 percent).

"Survival between these two groups differed, with 66 percent surviving 6 years in the first quartile compared with 83.8 percent in quartiles 2 through 4," the researchers were quoted as saying.

"In conclusion, our data show that in a cohort of patients with severe aplastic anemia receiving immunosuppressive therapy, telomere length was not associated with response but was associated with risk of relapse, clonal evolution, and overall survival."

SOURCE:  Journal of the American Medical Association (JAMA), September 22/29, 2010.