Breast cancer patients treated with taxanes-drugs like paclitaxel (Taxol) and docetaxel (Taxotere)-as part of their chemotherapy regimen have stronger immune systems one year after completing therapy than do women undergoing similar treatments without taxanes. The finding appears to turn conventional medical wisdom on its head.
Researchers in the Ohio State University Comprehensive Cancer Center studied 227 women enrolled in a multi-year study examining the relationship between stress and immunity in women with breast cancer. They divided the group into women who received taxanes as part of their treatment (55) and those who did not (172).
Researchers took blood from the patients and measured levels of key markers of the patients' immune status at two points in time-immediately after the women joined the study and one year following completion of treatment. Their analysis of the blood looked at the activity of the patient's T cells (white blood cells that can fight infections and cancer cells) and natural killer (NK) cells (another type of white blood cell that can kill cancer cells and cells infected with viruses).
They found that T cell growth was 37 percent higher and that the cancer killing activity of the NK cells was 39 percent higher in women receiving taxanes versus those who did not.
Scientists controlled for multiple variables that might contribute to the strength of the patients' immune function, including age, menopausal status, hormone receptor status, treatment, hormonal therapy at 12 months and cell counts, among others.
"This was totally unexpected," says Dr. William Carson, a surgeon and associate director of clinical research. "Most oncologists believe taxanes - just like the rest of the chemotherapeutic agents we use - suppress the immune system, not enhance it."
The study was published in the journal Clinical Cancer Research.
Carson says the research team had the ideal population to study, with the results of critical immune functions taken immediately after the patients' enrollment in the earlier study already on file. All of the women were part of an ongoing clinical trial at Ohio State running from 1994-2006 to study the effects of stress on the immune system among breast cancer patients with stage II or stage III disease.
Women in the study were assigned to either a stress-reduction group or an assessment group. Stress-reducing elements in the intervention group included periodic relaxation techniques and group support.
Halfway through the study, taxanes emerged as popular options for women whose disease had spread to their lymph nodes.
"These findings are important because they suggest taxanes may enhance a woman's ability to respond to infection or even to fend off a possible recurrence," says Carson.
On the other hand, T cell formation and NK cell function only partially reflect the vigor of a patient's immune system, and the relationship between the strength of a patient's immune system and the ability to fend off cancer is not yet completely understood.
"The real question is whether the use of taxanes improves patient outcomes or quality of life," says Carson. A study to assess that is already underway at Ohio State.
SOURCES:
Clinical Cancer Research, May 15, 2004
Ohio State University (http://www.osu.edu)
