- FRIDAY, May 16 (HealthDay News) — A simple blood test to check levels
of circulating tumor cells can help doctors more accurately assess how
well treatments are working in women with metastatic breast cancer,
according to a Georgetown University Medical Center study.

“It can take several weeks, and sometimes months, to determine if a
particular cancer treatment is working, because it can take that long to
observe any significant radiographic changes in tumor size or appearance,”
principal investigator Dr. Minetta Liu, of Georgetown's Lombardi
Comprehensive Cancer Center, said in a prepared statement.

“Right now, we have to rely on radiology studies such as CT scans,
ultrasound, and the like to determine whether or not there is disease
progression. With this new blood test, we have another reliable tool that
may allow us to determine much sooner if a therapy is ineffective, so that
we can change therapy earlier and potentially make more significant
improvements in survival,” Liu explained.

In this study, Liu and colleagues measured the number of circulating
tumor cells (CTC) in blood samples collected from metastatic breast cancer
patients every three to four weeks. The women were receiving various
treatments, including chemotherapy, endocrine therapy, and combination
therapy with a biologic agent.

The researchers found that 71 percent of patients with a CTC count of
five or greater had disease progression, compared with 66 percent of
patients with a CTC count of less than five.

“A CTC count of five or greater at the time of restaging was associated
with a 5.32-fold increase in a patient's chances of having disease
progression compared to CTC counts of less than five,” Liu said. “CTC
assessments should be used as a surrogate marker for treatment efficacy
and disease responsiveness. Changes in CTC results from less than five to
greater than or equal to five over time may herald disease
progression.”

The findings were released online May 15 in advance of the annual
meeting of the American Society of Clinical Oncology, in Chicago.

The study was funded by Veridex, LLC, which makes the technology used
in this study to measure CTC levels. Liu has received payments from
Veridex for speaking engagements.

More information

The U.S. National Cancer Institute has more about breast cancer treatment.