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.
The study
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.
The results
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% 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.
Going forward
"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.
