Dec. 10, 2010 (San Antonio) -- Women with metastatic breast cancer who have no tumor cells circulating in their blood after the first round of treatment live longer than those who do, French researchers report.
Circulating tumor cells, or CTCs, are cells that break off from a tumor and escape into the bloodstream. These cells can travel to other organs and establish new tumors.
Several studies have shown that higher levels of CTCs are associated with an increased risk for recurrence and death in metastatic breast cancer patients.
But the new study is the largest to look at the topic, and the CTCs predicted prognosis even after taking other markers of survival into account, says Jean-Yves Pierga, MD, PhD, professor of the medical oncology department at Institut Curie and Universite Paris Descartes, France.
The study also suggests CTCs can be used to monitor whether a woman is responding to treatment, he tells WebMD.
Pierga reported the findings at the annual San Antonio Breast Cancer Symposium.
Circulating Tumor Cells Predict Breast Cancer Progression
The study involved 267 women whose cancer had spread to other parts of their body (metastasized) and who were receiving chemotherapy with or without the targeted drug Avastin for the first time.
Before treatment, two-thirds of the women had one or more CTCs; 44% had five or more CTCs.
After two years, cancer had progressed in about 95% of those with five or more CTCs, compared with about 70% of those with fewer or no CTCs.
Looked at another way, women with five or more CTCs were 90% more likely to have their cancer worsen and nearly two-and-a-half times more likely to die, even after other tumor markers were taken into account, Pierga says.
Then the researchers looked at women's CTC levels after their first round of treatment. At two years, cancer had progressed in about 70% of those with fewer than five CTCs, but in all of those with more CTCs. Over 90% of those with fewer than five CTCs were still alive, compared with less than half of the women with more CTCs.
The study also showed that after three rounds of treatment, CTCs dropped more in women who received Avastin plus chemotherapy, compared with those who just got chemo.
Doctors Divided on Usefulness of CTC Testing
Still, doctors appear divided on whether CTC testing is useful.
Alison T. Stopeck, MD, director of the Clinical Breast Cancer Program at the Arizona Cancer Center in Tucson, says she doesn't use the CTC test at all.
"More often than not, I know which of my patients with metastatic breast cancer are progressing just by examining them," she tells WebMD.
Plus a high CTC count doesn't provide any information about what treatment might help, Stopeck says.
Minetta Liu, MD, director of translational breast cancer research at Georgetown Lombardi Comprehensive Cancer Center in Washington D.C., says the test is very useful.
"I use every tool I have," she tells WebMD. In some cases, knowing a woman has no CTCs allows her to delay much more expensive imaging tests to track the progress of the cancer, Liu says.