MAR 12, 2016 10:46 AM PST

Test Reveals Some Breast Cancer Patients Don't Need Chemo

WRITTEN BY: Xuan Pham
Chemotherapy is aggressive poisoning of rogue cells to cure cancer. But do all cancer patients benefit from this therapy? According to recent results of a new genetic test for breast cancer, the answer is no.
 
Genetic test reveals chemo is not necessary for all breast cancer patients

The test, called Oncotype DX, can identify patients in whom the breast cancers are more likely to be dormant. These women can thus be spared the agony of chemotherapy in favor of the less intense hormone therapy. Among the group of women that the test predicted to be at low risk for cancer recurrence, researchers reported 94% were alive and cancer-free at the five-year mark.
 
The Oncotype DX test is formally known as the 21-gene Recurrence Score assay. It works by analyzing the activity of 21 genes involved with breast cancer aggression and how these tend to respond after treatment. The outputs are scores that range from 0-100, with higher scores indicating worse prognoses.
 
In the study, German researchers recruited nearly 3,200 women with non-metastatic breast cancer that was also estrogen receptor positive and HER2 negative. About 15% of the women scored from 0-11, and were deemed at low recurrence risk even if other factors suggested otherwise; these patients received anti-hormonal therapies only. Of these women whose testing spared them of chemotherapy, 94% were living disease-free five years after their diagnoses.
 
Meanwhile, patients who scored between 12-25 were randomly assigned to one of two different chemotherapy treatments. These patients showed the same disease-free survival rates of 94% when treated with chemotherapy. Patients who scored above 25 received the same chemotherapy treatments and had 84% recurrence rate.
 
"These tests are able to define a substantial proportion of patients with very low recurrence risk who would not benefit from chemotherapy," said Oleg Gluz, first study author. In these women, skipping chemotherapy was the right call, as hormone therapy seemed to have nearly the same effect on cancer recurrence but without the damaging side effects.

Following the ideas of precision medicine, the Oncotype DX test is a new way to tailor treatments to individual breast cancer patients. Knowing those who will or will not benefit from grueling chemotherapy could save many patients from unnecessary side effects and costly treatments.
 
Although the results of this five-year study are promising and consistent with its three-year reports, some are still waiting on the survival rates at the 10-year mark. Genomic Health, the company that makes Oncotype DX, is already getting started on this follow-up study, and has plans to enroll more patients for other new combination therapy trials.
 

Additional source: US News Health
About the Author
I am a human geneticist, passionate about telling stories to make science more engaging and approachable. Find more of my writing at the Hopkins BioMedical Odyssey blog and at TheGeneTwist.com.
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