New blood test may save lives by detecting cancer's spread

December 6, 1999
Web posted at: 7:43 p.m. EST (0043 GMT)

In this story: Doctors: new test very sensitive and accurate Test made possible after protein discovery New study in the works RELATED STORIES, SITES

PHILADELPHIA (CNN) -- A new and possibly life-saving test may help doctors determine if colon-cancer patients are likely to have a recurrence of their disease.

A study conducted by Thomas Jefferson University and published Monday in the Annals of Internal Medicine suggests that doctors have found a genetic marker in colo-rectal cancer cells they can use to test for tiny pieces of the cancer that may have spread from the intestine to the lymph nodes.

Currently, most doctors check for cancer by looking through a microscope. But often cancer cells go unseen because they're too small for the naked eye.

	COLON CANCER
description risk symptoms treatment prevention Choose a link above to learn more about colon cancer. Source: WebMD

Even with a microscope, the human eye has trouble spotting cancer cells if they number fewer than five for every 100 normal cells.

Doctors say the new test is sensitive enough to detect a single cancer cell among 10 million normal cells. It may allow doctors to start treatment sooner, prolonging life for people who test positive.

"We actually used what is the most powerful way of finding a needle in a haystack in biology right now, and it's called RTPCR. And RTPCR stands for Reverse Transcriptase Polymerase Chain Reaction. It's a long word but RTCPR can amplify a single molecule one times ten to the tenth fold, which is an enormous amplification," said Dr. Scott Waldman, chief researcher of the project.

	VIDEO
CNN's Dr. Steve Salvatore reports on a new test that could give patients assurance that they are free from colon cancer. Real 28K 80K Windows Media 28K 80K

Finding cancer cells that have spread to the lymph nodes often determines whether chemotherapy is required. And accurate diagnosis traditionally has been a problem.

"It turns out that about 30 percent of the patients that are told that they don't have disease in their lymph nodes, about 30 percent of them will come back with recurrent disease within three to five years," Waldman said.

But the new test has proved to be very accurate, according to the study. One test group included 21 patients. Of that group, all 11 patients who had been free of cancer for at least six years tested negative. All 10 patients whose cancer had returned within three years of surgery tested positive.

The new blood test was made possible after scientists discovered that a protein called guanyl cyclase C, or GCC, was made by colo-rectal cancer cells. A test was designed to search the blood for the presence of GCC, helping doctors determine if cancer has spread from the colon to the lymph nodes.

But doctors said more research is needed. The test may be useful for diagnosing metastatic cancer. But that would only be determined through larger-scale clinical trials which follow new colo-rectal cancer patients through surgery and subsequent checkups.

"This was a retrospective study, conducted after the patients had been diagnosed -- we knew ahead of time what their diagnoses were and we specifically selected them," Waldman said.

The study was funded by the National Institutes of Health and Targeted Diagnostics & Therapeutics Inc., a private biotech firm co-founded by Waldman.

Next, he said he planned to enroll between 1,000 and 2,000 patients in a large, prospective five-year study comparing the ability of the standard histological examination of lymph nodes to that of the GCC marker test to predict recurrent disease.

Colo-rectal cancer is the third most common form of cancer and the fourth-leading cause of cancer deaths in the United States, where about 200,000 new cases are diagnosed each year.

Correspondent Dr. Steve Salvatore and Reuters contributed to this report.