"The number of CTCs before treatment can identify those patients
destined to live longer vs. those who will die sooner," says researcher
Neal J. Meropol, MD, director of the Gastrointestinal Cancer Program at Fox
Chase Cancer Center in Philadelphia.
The test also tells the doctor whether a person is responding to treatment
sooner than currently used measures, he says.
"The idea is to spare patients the side effects of ineffective therapies
by finding out who won't do well much sooner," Meropol tells WebMD.
CTC Levels in Colon Cancer Patients
The researchers tried out the test on 430 people with metastatic colon
cancer -- that is, cancer that had spread to other parts of the body such as
the liver or lungs.
Results showed that people with low CTC blood levels before treatment lived
more than twice as long as those with high levels: 19 months vs. nine
People with high levels relapsed much sooner: five months vs. eight
The results held up regardless of a person's age, type of treatment, extent
of disease, or overall health, Meropol says.
He adds that a high CTC level doesn't mean that a person won't respond to
therapy, just that the person "might not do as well as someone
The researchers also looked at what happened to people with high CTC levels
after they started treatment. They found that if CTC levels dropped
substantially within three to five weeks, the risk of relapse or dying did as
On the flip side, Meropol says, "If CTCs didn't clear from the blood
after a few weeks of treatment, the patient was destined to do poorly."
The findings were presented at the annual Gastrointestinal Cancers
Robert Mayer, MD, director of the Center for Gastrointestinal Oncology at
Dana-Farber Cancer Center in Boston, says other researchers have shown that
high CTC levels are associated with a poor prognosis in women with metastatic
The new findings offer "provocative, important pilot data [on their use]
in colorectal cancer," he tells WebMD.
Mayer says that before CTC screening is ready for prime time, however, it
needs to be tested in larger numbers of people.