A study published in the October 2012 Annals of Oncology compared levels of CTCs with levels of CEA (carcinoembryonic antigen) to see how the two tests compared or could be used together to predict survival times in metastatis CRC.
Results in 217 patients with metastatic CRC showed that at the beginning of treatment, CTC numbers alone–not CEA levels–could accurately predict length of survival. But when patients had a high initial level of CEA levels, adding the CTC number helped predict which patients would survive longer. At the 6-12 week mark, each test alone could accurately predict prognosis.
The study’s second author and member of FCRC’s Medical Advisory Board, Dr. Neal Meropol, noted that, in clinical practice, he tends to rely more on CT scans and MRIs for metastatic CRC treatment decisions, but that CTCs seem to be a good indicator for overall prognosis.For several decades, the level of carcinoembryonic antigen (CEA) in tumor tissue has been used to predict prognosis (length of survival) in early-stage colorectal cancer. Also, changes in CEA levels are often used to watch for cancer recurrence. However, there’s less evidence about how well CEA levels predict prognosis in metastatic CRC.
In an earlier study, this study’s authors showed that circulating tumor cells (CTCs) are another marker that accurately predict progression-free and overall survival in mCRC patients who are just starting therapy. In this second analysis, the researchers compared how well tests of CTCs and CEA levels—both separately and when used together—could predict survival in 217 mCRC patients at 55 centers in three nations. The tests were performed at the beginning of treatment, at 3-5 weeks and at 6-12 week time points.
At baseline (beginning of treatment), the CTC level aloneaccurately correlated with the person’s length of survival. Using both baseline tests together provided more information: A patient with a higher CEA level (≥ 25ng/ml) but low CTCs (≤3) had longer survival that those with more CTCs (20.8 versus 11.7 months). Both CTC and CEA levels could independently predict survival at 6-12 weeks after treatment was begun.
Second author Dr. Neal Meropol told FCRC that “I tend to rely more on CT scans and MRIs than CEA levels to make treatment decisions in patients with advanced colon cancer. One exception is the case of metastases that are difficult to measure accurately or to see at all on a scan: In those instances, the CEA test can help guide a decision.
“With regard to CTCs, these seem to be a good indicator of prognosis, but in my view there still isn’t enough evidence to use them to make decisions about changing therapy.”
Results of CEA tests are a common topic of both concern and comparison among cancer patients, especially in online chat discussions.
This study shows that the number of CTCs (circulating tumor cells in the bloodstream) can add another piece of information—at least in clarifying possible length of survival. But it’s only one more tool for your doctor to use, along with CEA levels, CT scans and MRIs, as well your overall condition and response to previous treatments.
As with all tests, it is a number, not a person nor an absolute predictor of how you will do with your cancer.
Sources: Annals of Oncology 00:1-9, 2012 ; personal communication with Dr. Neal Meropol, Chief, Division of Hematology and Oncology, Case Western Reserve University.