Tumor Test Helps Tailor Breast Cancer Treatments

A gene-based tumor test could identify women with a certain type of breast cancer who don’t need to undergo chemotherapy. The finding suggests that gene testing can add to traditional clinical testing to help guide treatment choices.

Breast cancer is the second most common cancer in U.S. women. Many with early stage breast cancer are advised to have chemotherapy in addition to other therapies, such as hormonal therapy. But some breast cancers don’t need to be treated with chemotherapy, which can be costly and have harsh side effects.

Researchers have been seeking ways to know which tumors would be most likely to respond to chemotherapy. One NIH-funded research team enrolled over 10,000 women in a clinical trial. The women had been recently diagnosed with a specific type of breast cancer (ER-positive HER2-negative cancer that hadn’t yet spread to the lymph nodes).

Many women with this type of breast cancer can be treated with hormone therapy alone. But it’s been difficult to distinguish these women from those who might benefit from chemotherapy as well.

The scientists tested how well a gene test could predict which women could safely avoid chemotherapy. The test analyzes tumor samples for the activity of 21 genesStretches of DNA, a substance you inherit from your parents, that define features such as your risk for certain diseases.. Based on the results, tumors are graded on a scale of 0 to 100; higher scores represent a greater risk of cancer recurrence.

The team found that 16% of the women had a score of 0 to 10, indicating a very low risk of recurrence. These women received standard hormone therapy but didn’t undergo chemotherapy. Five years later, their risk of breast cancer recurrence was less than 2%.

This shows that the test can clearly identify women with an early stage of this type of breast cancer who can safely avoid chemotherapy. Scientists are continuing to work on other diagnostic gene tests.