Blood tests for specific immune-response markers can predict the long-term disabling fatigue that affects a significant number of breast cancer survivors, according to an article in the May 1 issue of Clinical Cancer Research.

“These studies identify a biological basis for persistent fatigue in cancer survivors that is implemented by inflammation,” said Michael Irwin, MD, UCLA Semel Institute for Neuroscience, and the UCLA Jonsson Cancer Center.

“We have detected a biological marker that is a composite of two immune response elements,” he added. “This biomarker identifies - and can predict - which women have long term persistent fatigue. These findings point the way for development of novel treatment strategies that decrease this inflammatory response and thwart the fatigue that these patients endure.”

One component of the marker is a measure of the amount of interleukin-6 receptor circulating in the blood of patients compared with the amount of receptor on the membranes of monocytes, the normal and functional location.

In some survivors, a significant quantity of receptors is shed from monocytes and is found in blood plasma. Those free-floating receptors can still bind to circulating Interleukin-6, Irwin noted, and have the potential to interact with cells that normally don’t respond to cytokine/receptor activation - such as brain cells that may regulate fatigue sensation.

“IL-6 contributes to an activation of monocytes in the blood, and enables antigen presenting cells to activate T cells as part of the cellular immune response,” Dr. Irwin said.

The second component of the marker is an index measured by the level of T cells that are characterized by CD69, a cell membrane protein that indicates early activation of those T cells. Patients with a decreased number of CD69+ T cells along with the high ratio of serum IL-6R/monocyte-bound IL-6R were likely to experience persistent fatigue.

The current research is the first to document an association between biological mechanisms involved with the immune response and persistent fatigue.

“It is such an important quality of life issue. Many patients are surviving from their cancer treatments, but they are surviving with substantial impairments in their ability to carry on their lives,” Irwin said. “We’ve addressed the cancer in these survivors, and now we can also address the functional declines in the quality of life of these patients.”