The death rate for colorectal cancer has been dropping for more than 20 years, thanks to improved screening methods, according to the American Cancer Society. Yet it is still the second-leading cause of cancer-related deaths for men and women in the United States.
Colonoscopy screenings can prevent about two-thirds of colorectal cancers from developing by detecting precancerous polyps, said Dr. Ted Gansler, director of medical content for ACS. The ACS recommends men and women over the age of 50 should have a colonoscopy once every 10 years or a yearly fecal blood test.
"Unfortunately, only about half of people age 50 and older in the U.S. are up-to-date on their testing for colorectal cancer," Gansler said.
Dr. Donato Altomare and his colleagues hope to change that. The researchers have completed a small clinical trial on a breath test that screens for colorectal cancer using volatile organic compounds. The results of their study were published this week in the British Journal of Surgery.
Altomare believes patients would be more willing to take a screening breath test over a colonoscopy because the breath test would be quicker, less expensive and non-invasive.
Researchers tested 37 patients with colorectal cancer and 41 patients who had a clean colonoscopy. Patients who were receiving chemotherapy and/or radiation were excluded, as were patients with other colon issues like inflammatory bowel disease. Nineteen of the cancer patients had stage I or II cancer; 18 had stage III or IV.
Study participants remained in a room for 10 minutes to create equilibrium between their breath and the surrounding air. Their exhaled breath was then collected in a bag and processed to determine each individual's volatile organic compound, or VOC.
Using VOCs to diagnose cancer is a new frontier in cancer screening, according to the researchers. Scientists say tumor growth causes metabolic changes that lead to specific compounds that can be detected in exhaled breath. Ongoing studies are assessing the ability of a breath test to diagnose lung cancer, breast cancer, skin cancer and liver cancer.
No differences were found in the VOC profiles of patients in different stages of the cancer. The breath test analysis correctly identified 32 of the 37 patients with colorectal cancer and incorrectly diagnosed cancer in seven of the 41 healthy patients. Overall, the breath test had an accuracy rate of 76 percent in identifying patients with cancer.
The researchers concluded breath VOC analysis appears to have potential for detecting colorectal cancers, but further technical development is needed to improve the device's accuracy. Altomare said larger studies also need to be done to confirm the test's reliability.
"This is an interesting study, but a lot more research is needed before chemical analysis of exhaled breath might be added to the list of tests currently recommended for colorectal cancer screening," Gansler said.
Altomare and his team plan to use the breath analysis on patients with precancerous polyps to see if the test can detect them.
"The main goals of current screening tests are not just to find any colorectal cancer, but rather to find early -- curable - cancers and precancerous polyps that can be removed to prevent cancer from developing," Gansler explained.
Altomare also plans to study whether the test works on people who have other colon issues -- i.e., whether it can distinguish between cancer and inflammatory diseases. He is working with a professor in the chemical department at the University of Bari in Italy to create an electronic nose, "which we hope will further make the colorectal cancer screening by breath analysis more easy and available as a screening tool for the general population."
In the meantime, Gansler urges people to take advantage of screening methods that are already available and have been proven to be effective in saving lives.