Underused cancer test could improve treatment for thousands

Using data from the National Cancer Database for 40,844 patients, Mayo Clinic physicians and scientists teamed up to look at benefits of a blood test that measures the protein called carcinoembryonic antigen, or CEA, in stage 2 colon cancer. Carcinoembryonic antigen can be found in higher levels in people with certain cancers, especially colon cancer.

The researchers found that knowing these blood test results prior to treatment could have changed the classification for 17 percent of stage 2 colon cancer patients from average risk to high risk. That change could have altered treatment options, including whether to use chemotherapy.

"The decision to give a patient chemotherapy after surgery is not a light one, and physicians must weigh the risks and benefits," says senior author Kellie Mathis, M.D., a Mayo Clinic colon and rectal surgeon. "We are currently using the blood test to help make these difficult decisions, and we suggest other physicians do the same."

The blood test has been around for decades but is not broadly used across the country. It was recorded in 54 percent of cases meeting other relevant criteria for the study. While in some cases the test may not have been entered in the database, many other patients may not be getting it.

"There is no good reason for a physician to omit this blood test, and more work needs to be done to ensure that all patients receive it," Dr. Mathis says.

When patients get the blood test, the authors point out it is often done after surgery to monitor the cancer's development. Greater, and earlier, consideration of protein level may be warranted, the researchers say.

Colorectal cancer is the fourth most common cancer in the U.S. and the second deadliest.

There are four primary stages of colon cancer. Generally, with stage 2, the cancer hasn't spread to nearby lymph nodes or distant organs but has grown into or through the wall of the colon. Some stage 2 patients fare worse than some stage 3 patients, who usually benefit most from chemotherapy. But the research team believes this blood test can help determine which stage 2 patients are at a higher risk and therefore could benefit from therapy.

The researchers also discovered that, for stage 2 patients who had surgery but not chemotherapy, the five-year survival rate was 66 percent for those with elevated protein levels and 76 percent for those without elevated levels. And for patients with elevated protein levels, those who had chemotherapy and surgery fared better than those who only had surgery.

"If a patient with a new diagnosis of stage 2 colon cancer has an elevated carcinoembryonic antigen level, physicians should consider chemotherapy in addition to surgery," says Dr. Mathis.