A Blood Test for Breast Cancer?

I understand that there’s a new blood test for breast cancer that is a big breakthrough. Who should have it? When?

– October 6, 2005

A promising new test for breast cancer patients can count malignant cells in the bloodstream and thus tell doctors whether or not treatment is working. The fewer cancer cells found, the better the outlook, and vice versa. The test is not for screening healthy women for the disease. At this time, it is intended only to assess the status of women who are already being treated in order to help make decisions about whether additional treatment is needed.

The test method was studied at 20 medical centers in the United States, and results were published in the August 19, 2004 issue of the New England Journal of Medicine. A total of 177 women took part, all of whom already had stage 4 breast cancer, the most advanced form of the disease.

Until now, doctor and their patients typically had to wait months before doing bone scans or x-rays to see if a particular treatment was working. The new test reportedly will reduce the waiting time to just weeks.

Cells from malignant tumors can break off and travel through lymphatic and blood vessels. Cancer spreads when these cells begin to grow in other areas of the body far from the spot where the disease originated, a process called metastasis. Once this happens, cancer becomes much harder to treat, and the chances for a cure decrease. If the new test shows that a woman has no circulating cancer cells, she may not need further treatment. If the test shows that lots of cells are circulating, more aggressive treatment is indicated.

Researchers also plan to investigate whether the new test also works for patients with colon, lung and prostate cancer.

Andrew Weil, M.D.

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