Breast Cancer: Blood Test Spots Wayward Tumor Cells

June 5, 2012— -- A simple blood test can help predict the recurrence of breast cancer, a new study has found. The question is: Will it save lives?

The test detects cancer cells in the blood that have broken free from a tumor in the breast, like seeds that have fallen from a tree.

"The greater the number of seeds you sow, the greater the chance they'll take hold and grow," said study author Dr. Anthony Lucci, a surgical oncologist at the University of Texas MD Anderson Cancer Center in Houston.

Lucci and his team followed more than 300 women diagnosed with non-metastatic breast cancer for up to eight years, and found those who had cancer cells in their blood were five times more likely to relapse or die from breast cancer. Women with high levels of circulating tumor cells were 10 times more likely to relapse or die during the study period.

The results, published today in The Lancet Oncology, could help identify breast cancer patients with a high risk of recurrence. But the jury's still out on whether those patients should be monitored more frequently or treated more aggressively.

"I think we need to be patient," said Lucci, stressing the need for clinical trials to tease out the test's true value. "The natural urge is to run the test; have more information. But we don't know how best to use that information."

The test can reliably detect a single cancer cell in 7.5 milliliters of blood. But to become a tumor, that cell has to evade the body's immune system and find the perfect environment to grow and divide.

"In ongoing studies we're trying to characterize the cells that break free; figure out which ones are capable of setting up shop," Lucci said.

Nearly one-quarter of the women in the study had cancer cells in their blood, according to the study. But only 15 percent of them relapsed after undergoing treatment, meaning the vast majority did not.

"We don't want to over-treat people," said Lucci, alluding to the ongoing debate about cancer screening tests and whether they do more harm than good. "But if we can get information that helps us guide therapy in subsets of patients, that would be really useful."

Breast cancer treatment is currently guided by the size of the primary tumor, whether it has spread to lymph nodes or other organs, and molecular markers, like HER2, that open the door for targeted chemotherapies. But Lucci said cancer cells in the blood may be molecularly different from those in the primary tumor.

"We detected HER2-positive cells in the blood of patients with HER2-negative tumors," said Lucci, describing the results of a separate study he recently presented at the American Society of Clinical Oncology meeting in Chicago. "It raises the question of whether those patients could potentially benefit from other therapies."

But experts say it's too soon to tell whether having a single blood-borne cancer cell should influence treatment decisions.

"There's a substantial amount of interest in the technology of counting circulating tumor cells in the blood, but it's still a relatively new technology and questions remain as to how it can best guide clinical practice," said Dr. Len Lichtenfeld, deputy chief medical officer for the American Cancer Society. "At this point in time, it's difficult to say this technology would improve the care of women with breast cancer."

Until the test is proven to provide information that can refine and improve care for women with breast cancer, it's not ready for prime time, Lichtenfeld said. "This information is interesting, but ultimately it's how it impacts patient care that's most important."