Three genomic tests—of prognosis, of sensitivity to chemotherapy, and of sensitivity to hormone therapy—separately predict the likelihood of recurrence of breast cancer if no treatment follows the surgery, and the cancer's vulnerability to chemotherapy or hormone therapy, says a report.
Dr. W. Fraser Symmans, a professor at the Department of Pathology, The University of Texas M. D. Anderson Cancer Center, says that each predictor is independent of the others, providing unique information to physicians and patients considering treatment options.
"Existing genomic tests for breast cancer provide information about future risk in general, but not the likely benefit of each treatment option separate from a patient's overall prognosis if no treatment followed surgery. It is important to independently assess these three variables," says the researcher.
Symmans will present results from two studies involving 960 patients validating a 200-gene index that predicts a patient's response to hormone-suppressing therapy. In the two studies, the Sensitivity to Endocrine Therapy (SET) Index score predicted distant relapse free survival among 453 patients who received tamoxifen, an anti-estrogen therapy, for five years.
The index did not predict prognosis among 507 patients who did not receive hormone therapy. "We believe this is the first genomic test to predict sensitivity to hormone therapy independent of a patient's prognosis if no post-surgical treatment is received," Symmans says. "A patient with ER-positive breast cancer probably still would choose to receive hormonal therapy, but better understanding of their cancer's sensitivity to endocrine therapy would help patients and their doctors decide on a treatment strategy," Symmans adds.
Pusztai will present a poster showing what the three predictors reported in two groups of breast cancer patients. "These three predictors were developed and validated separately, now we've put them together for the intended purpose - to provide all the necessary information for physicians and patients to decide on the best therapy or combination of therapies for breast cancer from a single assay," Pusztai says.
The three clinical outcome predictors include a 76-gene prognostic test that indicates whether a patient is at high or low risk of the cancer recurring after surgery, a 30-gene predictor of the cancer's sensitivity to chemotherapy, and the 200-gene index (SET) of sensitivity to hormone (endocrine) therapy.
Pusztai says that the predictors will help guide the decision whether to follow surgery with chemotherapy, endocrine therapy, both, or neither. A planned prospective clinical trial at M. D. Anderson will use the three predictors to select treatment options for new patients. "Let's say a new patient has a needle biopsy performed, and the microarray analysis of the tumor's gene expression predicts she is at low risk of recurrence and also has cancer that is insensitive to both chemo- and endocrine therapies; in this cases the best option is relatively clear; surgery alone," Pusztai says.
"However, it is important to know the sensitivity of the cancer to chemo- or endocrine therapies independent of the risk of recurrence alone. For example, a person even with low risk for cancer recurrence might elect to receive further therapy if her cancer is known to be highly susceptible to treatment," the researcher says.