February 18, 2009

New Screening Method Detects Hidden Colorectal Cancers

U.S. researchers said on Tuesday that more sensitive screening tests may one day help doctors determine how far colorectal cancer has spread, giving patients a better shot at survival, Reuters reported.

A genetic test that searches for a specific cancer biomarker known as guanylyl cyclase 2 C found hidden cancer in lymph nodes that current screening methods failed to pick up, they reported.

The American Cancer Society said colorectal cancer is the fourth most common cancer in men and the third in women worldwide, striking 1.2 million people each year.

Dr. Scott Waldman of Thomas Jefferson University in Philadelphia, whose study appears in the Journal of the American Medical Association, said one of the unmet needs of colorectal cancer is an accurate staging method to determine how far the disease has spread.

Waldman is a scientific adviser to Targeted Diagnostics and Therapeutics Inc. in Pennsylvania, which helped fund the study and has a license to make diagnostic tests based on the research.

Doctors currently test for the cancer by examining a small sample of tissue from lymph nodes. However, the cancer comes back in about 25 percent of patients whose lymph nodes test clean.

The new study was an attempt to secure a test that looks for the protein guanylyl cyclase C, a marker in lymph nodes associated with increased risk of recurrence of colorectal cancer, that doctors hope might do a better job at finding these hidden cancers.

Waldman and others found during previous studies that this protein is present only in the intestinal wall and in colon cancer cells. Therefore finding it in lymph nodes would suggest the cancer has spread.

The researchers studied 257 people with colorectal cancer whose biopsies detected no cancer in the lymph nodes closest to where their tumors had been surgically removed.

They were able to find the cancer biomarker in 87.5 percent of patients tested using the genetic test. Almost 21 percent had their cancer come back, compared with only 6.3 percent of those patients whose lymph nodes tested negative for the cancer biomarker.

"The findings suggest the more sensitive test might help spot cancers missed in biopsies, but larger studies would be needed to tell how effective the test might be," Waldman said.


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