NEW YORK – People who are diagnosed with colon cancer after routine colonoscopies tend to have better outcomes and less advanced cancers than people diagnosed based on symptoms, says a new study.

Those who were diagnosed with colon cancer as a result of symptoms were three times more likely to die during the study than the patients diagnosed after colonoscopy screenings, researchers found.

“It’s in line with its current use. It shows that colonoscopy appears to be beneficial in reducing deaths in those diagnosed with colorectal cancer,” said Dr. Chyke Doubeni, who studies colonoscopy use but wasn’t involved in the new research.

Colon cancer is the third most common cancer and the second leading cause of cancer death in the U.S., according to the government-backed U.S. Preventive Services Task Force (USPSTF), which recommends that people between ages 50 and 75 get screened by colonoscopy every ten years.

During a colonoscopy, a doctor uses a long flexible tube equipped with a tiny video camera to see the interior of the colon.

According to the study authors, the incidence of colon cancer in the U.S. has dropped by about 6 percent since the first national colonoscopy guidelines were introduced in 2000 – mostly due to doctors catching and removing precancerous polyps during screening.

Still, the U.S. Centers for Disease Control and Prevention reports that about 22 million people are not up-to-date with their colon cancer screenings.

For the new study, Dr. Ramzi Amri and colleagues from Massachusetts General Hospital and Harvard Medical School in Boston analyzed data on all people who underwent colon cancer surgery at their hospital from 2004 through 2011.

Their goal was to see whether those diagnosed with colon tumors after colonoscopy screenings had better outcomes than patients diagnosed after going to their doctors because they were experiencing symptoms, such as bleeding from the rectum.

Amri and his colleagues had data on 217 people diagnosed after screening and 854 who were diagnosed based on symptoms or other tests.

They found that in addition to being more likely to die, patients diagnosed with colon cancer based on symptoms were far more likely to have advanced disease, to have cancer that spread to other parts of their bodies and to have cancer that recurred.

About 75 percent of patients diagnosed based on their symptoms had advanced disease, compared to about 38 percent of those diagnosed after colonoscopy screenings.

About 11 percent of the group diagnosed with symptoms had cancer that spread to other parts of their bodies and 12 percent had recurrences, compared to about 2 percent and 6 percent, respectively, in the colonoscopy group.

“This further emphasizes the important role compliance to screening colonoscopy guidelines can play in prolonging longevity, improving quality of life, and reducing health care costs through early detection of colon cancer,” the researchers write in JAMA Surgery.

“This definitely supports the practice that we should be screened for colorectal cancer, but I wouldn’t go as far to say colonoscopy is the only thing that should be used,” Doubeni, of the University of Pennsylvania’s Perelman School of Medicine, said.

The USPSTF also gives people the option of annual high-sensitivity fecal occult blood testing or sigmoidoscopy – similar to a colonoscopy – every five years combined with high-sensitivity fecal occult blood testing every three years.

The new study’s authors do acknowledge some of its limitations, including the fact that their data was drawn from a hospital that receives more severe colon cancer cases from other hospitals, which means the results may have exaggerated the differences between the two groups.

Aside from costing between $600 and $800, colonoscopies are not risk free. Doubeni said people may experience some discomfort and that there is also a very small risk of the scope perforating the colon.