Circulating tumor cells (CTCs) are cells that break off from a cancer tumor and move into the blood stream. Doctors think that CTCs mean that breast cancer cells may be active in areas of the body besides the breast.
The number of CTCs in the bloodstream has been linked to prognosis in people diagnosed with metastatic breast cancer (cancer that has spread to one or more parts of the body away from the breast, such as the bones or liver). Higher levels of CTCs are linked to worse outcomes in women diagnosed with metastatic breast cancer.
CTCs seem to be a marker of prognosis. So doctors wondered if switching chemotherapy regimens if the first didn’t lower CTC levels would lead to better outcomes. Unfortunately, the results were disappointing. Switching chemotherapy regimens didn’t improve the outcomes of women diagnosed with metastatic breast cancer with high levels of CTCs.
The study, “SWOG S0500 -- A randomized phase III trial to test the strategy of changing therapy versus maintaining therapy for metastatic breast cancer patients who have elevated circulating tumor cell (CTC) levels at first follow-up assessment,” was presented on Dec. 13, 2013 at the 2013 San Antonio Breast Cancer Symposium.
The study involved 123 women newly diagnosed with metastatic breast cancer who also had high CTC levels. A high CTC level was 5 or more CTCs per 7.5 ml of blood. The women had been prescribed a chemotherapy regimen by their doctors, but after 21 days on the chemotherapy regimen, the women’s CTC levels hadn’t dropped. So the researchers randomly assigned the women to either stay on the same chemotherapy regimen or switch to a new regimen selected by their doctors.
The researchers then compared the two groups’ overall survival (how long the women lived, with or without the cancer growing) and progression-free survival (how long the women lived without the cancer growing).
Survival rates were about the same whether or not the women switched chemotherapy regimens:
- overall survival was about 1 year in both groups
- progression-free survival was 3.5 months for women who switched regimens and 4.6 months for women who didn’t switch
While these results don’t seem very promising, the researchers were quick to point out that they don’t mean that chemotherapy doesn’t benefit women diagnosed with metastatic disease with high levels of CTCs. Instead, the researchers suggested that these women may need more aggressive treatment strategies than were used in the study, such as new medicines being tested in a clinical trial.
"Although chemotherapy may work for these patients, it clearly does not work as long as one would like,” said Jeffrey Smerage, M.D., clinical associate professor at the University of Michigan Comprehensive Cancer Center, who presented the research. “This suggests that this patient population needs more effective treatment options beyond traditional chemotherapy. Given that these patients have higher cancer-related risks, early consideration of clinical trial participation would be appropriate."
If you’ve been diagnosed with metastatic breast cancer and tests show you have a high level of CTCs, you might want to talk to your doctor about this study. Ask if your CTC levels will be checked again after your first cycle of chemotherapy and what your treatment options are if CTC levels haven’t dropped. You also may want to ask your doctor about any clinical trials that may be a good fit for you and your unique situation.
For more information on clinical trials, as well as how to find one that might be right for you, visit the Breastcancer.org Clinical Trials pages.