A new genetic test may be able to predict a woman's chance of survival after chemotherapy for breast cancer, according to a new study.

In the future, such a test could indicate which patients would benefit most from chemotherapy and which might consider seeking an alternative treatment, such as enrollment in a drug trial, the researchers say.

Currently, 30 to 40 percent of women treated with chemotherapy for breast cancer actually benefit from it. A diagnostic test could help distinguish which women would benefit, said study researcher Dr. W. Fraser Symmans, a professor at The University of Texas MD Anderson Cancer Center in Houston.

"For some [patients] it would provide an affirmation that chemotherapy would really help them," Symmans told MyHealthNewsDaily. For others, the results may suggest a less robust response to chemotherapy. This result doesn't necessarily mean women should abandon chemotherapy completely, but that they perhaps should consider an additional or alternative treatment, Symmans said.

The new study, published in the May 11 issue of the Journal of the American Medical Association, is preliminary, and further research is needed to validate the results. But such a test would advance the field of personalized medicine , or the practice of tailoring medical therapies to an individual based on their genes or genes of their cancer.

Such tests are just beginning to be used in a few rare cases. For instance, last month, researchers reported a case in which a patient's leukemia treatment was changed based on the results of a genetic test.

Chemotherapy for breast cancer

The study involved only patients with so-called HER2-negative breast cancer. This means the patients' breast cancer will not respond to the drug Herceptin. About 80 percent of women with breast cancer are HER2-negative.

The researchers first studied a group of 310 women who underwent chemotherapy for their breast cancer. Some women also underwent hormonal therapy after their chemotherapy.

The researchers looked to see whether the patients' cancer was resistant to chemotherapy, meaning a lot of cancer remained after chemotherapy treatment. They also assessed the patients' survival three years after the chemotherapy. Then, they examined the DNA of the patients' cancer in order to find genetic signatures that were correlated with the patients' outcome.

Finally, the researchers designed a genetic tests based on their initial study. They assessed the accuracy of the test on a separate group of 198 breast cancer patients.

The test essentially asks three questions: Will the cancer respond to hormone therapy? Is the cancer resistant to chemotherapy? Will the patient have an outstanding response to chemotherapy in terms of their survival?

Predictive test

The test had a positive predictive value of 56 percent. This means that if the test predicts a patient will have an outstanding response to chemotherapy, 56 percent of the time, the patient will have this response, Symmans said.

Patients predicted to be responsive to chemotherapy had a fivefold reduced risk of developing cancer at another site in the body within three years.

About 28 percent of patients in the study were predicted to respond well to chemotherapy. There was a 92 percent chance that these patients would not relapse within three years meaning they would not develop cancer at another site in their body within this time.

The researchers will continue to develop their test by studying additional groups of patients.

If doctors one day use the genetic test, it might boost enrollment in trials that test new treatments for breast cancer. Currently, few breast cancer patients believe they should go into clinical trials, Symmans said.

"If there's a validated test that demonstrates that potentially, [an alternative therapy] might help you more, more and more people might consider participating in the advancement of treatment development," by enrolling in clinical trials, Symmans said.

Pass it on: A new genetic test may help guide treatment for some breast cancer patients.

Follow MyHealthNewsDaily staff writer Rachael Rettner on Twitter @RachaelRettner.