Early research suggests that an existing blood test could help determine which patients with early-stage breast cancer, who had their tumors surgically removed, may see their cancer come back. If further testing validates this new research, it could mean some women would get more aggressive cancer treatments than currently prescribed.

Doctors at the M.D. Anderson Cancer Center in Houston, Texas, took blood samples from 302 women with stage 1, 2 or 3 breast cancer right before they had their tumor surgically removed. None of the women had been treated with chemotherapy. The patients' progress was followed for nearly 3 years (35 months).

According to the study published Tuesday in the journal Lancet Oncology, 25% of women whose cancer was confined to the breast had at least one circulating tumor cell in their 7.5 milliliter sample of blood (about the equivalent of half a tablespoon). Normally a lymph node biopsy is used to determine the likelihood of the cancer coming back.

Researchers found 73 women (24%) had at least one circulating tumor cell; 29 women (about 10%) had at least two circulating tumor cells in their sample and 16 (5%) had at least 3 or more tumor cells in their blood sample.

Women with early stage breast cancer aren't usually thought to be at high risk for having their cancer come back, but some do and doctors don't know why, which is why lead study author Dr. Anthony Lucci says he and his colleagues decided to investigate this.

The study found that if a women had just one circulating tumor cell in her sample, she had a 4 times greater chance of dying, compared to a woman with no CTCs.

"If three or more tumor cells were found in a blood sample, the woman had an almost 11 times higher risk of dying from the cancer compared to those who didn't have any circulating tumor cells," says Lucci.

All in all, 31% of the women in this study found their cancer came back or died during the study period.

Lucci likens circulating tumor cells to seeds in a garden. If you dump a bag of seeds in the dirt, he says, the odds that one or several take hold and grow is much higher than planting just one seed.

"While the findings of an association between circulating tumor cells and outcome in breast cancer is not novel," says Dr. Boris Pasche, Director of the Division of Hemotology and Oncology at the University of Alabama at Birmingham. "The strength of this new paper is its capability to characterize the magnitude of the impact of CTCs on breast cancer outcome." He says the other strength of this study is that the blood samples were taken just before surgery, giving a more accurate picture of where traces of cancer are outside the breast.

Once a tumor is removed, it's possible for cells to break off, thus skewing the accuracy of how much cancer is already circulating outside the breast.

According to a commentary in the Journal of the American Medical Association in March 2010, the first documented research on circulating tumors was conducted in 1846. Since then, studies have shown that looking for circulating tumor cells in patients, who've already seen their cancer spread, can be an important tool to determine how a patient does in the future.

This hasn't been proven to be the case for early stage breast cancer, where the cancer has not spread beyond the breast and it is something this new study doesn't do either.

However, Pasche, who was not involved with the research, says if the results are validated in larger clinical trials, this may lead to a new screening method for predicting which women may be more likely to see their cancer come back.

"This provides a new train of thought of how we should handle women with early-stage breast cancer because we could identify the women who have a high risk of recurrences and early death and treat them differently." Pasche suggests those patients get more aggressive removal of lymph nodes, they may be put on chemotherapy (something they may not normally be prescribed) and their doctors will probably have a much tighter follow-up schedule for them.

Lucci and Pasche say this type of screening is not yet ready for prime time, and M.D. Anderson already has further studies underway.