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DNA Test Shows Promise for Breast Cancer Care

Blood sample helps doctors assess treatment response, researchers say

WebMD News from HealthDay

By Amy Norton

HealthDay Reporter

WEDNESDAY, March 13 (HealthDay News) -- An experimental blood test could help show whether women with advanced breast cancer are responding to treatment, a preliminary study suggests.

The test detects abnormal DNA from tumor cells circulating in the blood. And the new findings, reported in the March 14 issue of the New England Journal of Medicine, hint that it could outperform existing blood tests at gauging some women's response to treatment for metastatic breast cancer.

That's an advanced form of breast cancer, where tumors have spread to other parts of the body -- most often the bones, lungs, liver or brain. There is no cure, but chemotherapy, hormonal therapy or other treatments can slow disease progression and ease symptoms.

The sooner doctors can tell whether the treatment is working, the better. That helps women avoid the side effects of an ineffective therapy, and may enable them to switch to a better one.

Right now, doctors monitor metastatic breast cancer with the help of imaging tests, such as CT scans. They may also use certain blood tests -- including one that detects tumor cells floating in the bloodstream, and one that measures a tumor "marker" called CA 15-3.

But imaging does not tell the whole story, and it can expose women to significant doses of radiation. The blood tests also have limitations and are not routinely used.

"Practically speaking, there's a huge need for novel methods" of monitoring women, said Dr. Yuan Yuan, an assistant professor of medical oncology at City of Hope cancer center in Duarte, Calif.

For the new study, researchers at the University of Cambridge in England took blood samples from 30 women being treated for metastatic breast cancer and having standard imaging tests. They found that the tumor DNA test performed better than either the CA 15-3 or the tumor cell test when it came to estimating the women's treatment response.

Of 20 women the researchers were able to follow for more than 100 days, 19 showed cancer progression on their CT scans. And 17 of them had shown rising tumor DNA levels. In contrast, only seven had a rising number of tumor cells, while nine had an increase in CA 15-3 levels.

For 10 of those 19 women, tumor DNA was on the rise an average of five months before CT scans showed their cancer was progressing.

"The take-home message is that circulating tumor DNA is a better monitoring biomarker than the existing Food and Drug Administration-approved ones," said senior researcher Dr. Carlos Caldas.

It all suggests that the test could help in monitoring women's treatment response, said Yuan, who was not involved in the study.

But while she said the findings are "exciting," she also stressed that a lot more work needs to be done.

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