New screening model for colon cancer may improve survival rates

Jun 29 2006

Scottish researchers have come up with a method of identifying people who are at risk of certain types of hereditary colon cancer.

They have developed a two-stage screening model which can genetically identify those with hereditary cancers and say it will also help influence treatment choices for those already diagnosed with colon cancer.

The researchers from the University of Edinburgh say the method allows for a rapid assessment of whether any patient newly diagnosed with bowel cancer has a mutation.

This year, colorectal cancer will affect as many as 150,000 people in the United States and 500,000 worldwide and the outcomes of the disease could be prevented if more was known about the risk of colorectal cancer developing and effective preemptive action was applied.

Colon cancer is the third most common cancer, and more than 55,000 people in America alone die each year from the disease.

Around 3 to 4 percent of cases of colorectal cancer occur in the familial cancer syndromes and the most common is the Lynch syndrome which is caused by a germ-line mutation in one of four DNA mismatch-repair genes.

There are apparently complicated molecular changes that occur in colon cancer which are difficult to detect and some hereditary cancers are missed even when these tests are used.

The Scottish researchers aimed to improve upon the existing screening techniques so for the study they recruited 870 people newly diagnosed with colon cancer, all under age 55 at the time of diagnosis.

This in itself indicates a higher-than-average risk of hereditary colon cancer as almost all colon cancers are diagnosed in people over age 50.

Then, regardless of family history, age, and other personal details, the researchers examined blood and tumor samples to look for mutations in the study volunteers' DNA that would increase the risk of colon cancer and found that 4 percent of those in the study had such mutations.

With the information received the researchers were then able to develop the two-stage model which they used on a sample of 155 people.

The researchers found 62 percent of the known genetic mutations responsible for hereditary cancers.

They believe being able to pinpoint who has the genetic mutations common in familial colon cancer can help physicians decide upon treatment.

Although survival rates did not differ between the groups the tests were carried out after people had been diagnosed with colon cancer.

Experts say the real benefit from the model would come from its ability to assess an increased risk in people who have not yet been diagnosed and then survival rates might be affected.

Experts stress the importance of a colonoscopy for anyone over age 50, but for those with a family history of colon cancer, colonoscopy screenings should start earlier.

The study is published in the current issue of the New England Journal of Medicine.