It’s no coincidence that I’m talking to you today about colon cancer as March 2015 marks the 15th anniversary of Colon Cancer Awareness Month. In celebration of this month-long event, and in solidarity for those affected by colon cancer or who have family members with the disease, people around the nation, particularly gastroenterologists, will be wearing all blue.
In the last decade or so, cancer-related deaths between the ages of 40 and 80 have surpassed those of cardiovascular disease. For males in that age spectrum, cancer of the colon or large intestine and rectum runs second to that of lung cancer as a cause of cancer-related death. In women, breast and lung cancer are numbers one and two, while colorectal cancer runs a close third. In the USA, about 160,000 new cases are diagnosed annually and almost a third die of their disease.
Since the development of colonoscopy over 40 years ago and its nearly universal availability, it has become accepted as a well-tolerated and highly accurate diagnostic and screening procedure for asymptomatic patients at risk for this disease. Only a few decades ago the general sentiment among many individuals was that “if it works, don’t fix it, don’t look for problems.”
With better technology and assessment of the risks versus benefits of colon cancer screening methodologies, it has now been accepted widely. Today over 60% of those people deemed of average risk due to age over 50, or at increased risk due to family history of colon cancer, polyps and chronic colitis, are undergoing tests in the absence of symptoms. Common presentations of colorectal cancer include rectal bleeding, abdominal pain, altered bowel habit, weight loss and narrowing of stool diameter.
Some have occult blood in the stool on submitted chemically impregnated cards, anemia or iron deficiency, jaundice or recurrent fevers in the absence of infection. A palpable abdominal mass and history of dark red rectal bleeding are highly predictive findings suspicious for colon cancer. It is important, however, to remember that benign conditions can mimic those of colorectal cancer, and the best strategy at any age is diagnostic colonoscopy, with or without CAT scan or MRI imaging studies.
About 20% of individuals have disease at an advanced stage at the time of diagnosis. Those without weight loss, jaundice, rectal bleeding or anemia have a much better prognosis. The best course of therapy is prevention. We have better knowledge today of pre-malignant polyps in the colon and rectum, genetic factors, familial inheritance patterns of colon cancer and the natural history of disease. Occult blood testing has had a favorable impact in selecting individuals in need of more urgent colonoscopy, and there have been improvements with immunochemical and fecal DNA tests.
Eighty percent of the time, affected people are the first diagnosed with this condition in their family. Since the vast majority of these cancers begin as polyps, and for most there is a long lead time between their development and evolution to cancer, interventions to diagnose these lesions before they turn malignant are key in the war against this major killer. Waiting until symptoms arise translates into a higher likelihood of advanced disease at time of diagnosis and death.
For those intolerant of colonoscopy, CT colonography colonoscopy is an alternative with limitations. The accuracy of colonoscopy exceeds 95%, and our goals today are to get over 80% of those at risk enrolled in screening and surveillance programs after the removal of pre-malignant polyps. Over 90% of patients with colon cancer are over the age of 50, however we are seeing a change in this cancer’s biology and predilection for younger age groups.
Our expanded knowledge of polyp subtypes, their risks for subsequent cancer in and implications for their first-degree relatives, and detection and removal techniques have significantly improved. About 3-5% of colon cancers occur in genetically predisposed individuals with identifiable syndromes that help us in identifying individuals with markedly increased risks of colon and other cancers at significantly younger ages.
Despite progress in instruments, bowel cleansing regimens, improved polyp detection and removal techniques, diagnosis, imaging studies, tumor markers, surgery, chemotherapy agents and radiation therapy, our goal today should be early detection and prevention. Obesity, smoking and type II diabetes mellitus increase the risk of colon cancer, African Americans get colon cancer at an earlier age and present with more advanced disease at the time of diagnosis, and that aspirin, similar agents, folate and vitamin D may be helpful in some populations at increased risk. Several organizations recommend initiation of colon cancer screening in African Americans at age 45.
Despite rare risks with colonoscopy, almost 1 in 20 non-investigated individuals will get colon cancer during their lifetime, far exceeding the risks of diagnostic testing. The data has been so convincing in long-term studies that virtually all third-party insurers guarantee coverage for screening colonoscopy.
In short, an ounce of prevention is worth a pound of cure. Colonoscopies save lives, so be sure to talk to your doctor about when you should get screened for colon cancer.