New Colorectal Cancer Screening Tools
Each year cancer of the colon and rectum kills an estimated 56,000 Americans. However, it is one of the most curable cancers if caught early. CBS News Medical Correspondent Dr. Emily Senay takes a look at two new ways doctors can detect the disease. Both are less painful and less embarrassing than traditional techniques.
Dr. Senay says early detection is crucial is and that means getting screened. Right now, the most effective method is getting a colonoscopy. It's a rather unpleasant, invasive procedure that examines the colon using what's called a scope. But, a study published in today's journal Gastroenterology found that a new technique using DNA shed from the colon was 91% effective in detecting the disease, and new technology may allow doctors to perform "virtual" colonoscopies.
New vs. Old Screening Tools
The first test examines colon cell DNA from stool samples for abnormalities associated with colorectal cancer and precursor lesions. After the patient takes his or her own sample and submits it to the physician, researchers extract colon cell DNA and examine it with EXACT's gene-based screening tool. Certain DNA qualities and quantities associated with colon cancer are the focus of EXACT's analysis. The cost is expected to be much cheaper than a colonoscopy, which vary in cost from $1,000 to $2,500. It's expected to be available in two years.
The second new treatment, virtual colonoscopy, is an alternative to enemas, sigmoidoscopy and colonoscopy for colon cancer screenings. It's a procedure that uses CT scanning technology to obtain a detailed look at the interior of the colon without anesthesia, lab work or the discomfort. The virtual colonoscopy detects precancerous polyps and cancerous lesions as small as 6mm. One company offering the technology is InsideTrac. They're also using this technology to screen for other health problems like heart disease and other cancers.
Physicians currently use fecal occult blood testing (FOBT), flexible sigmoidoscopy, or the colonoscopy for detection. The FOBT looks for blood in the stool that might be associated with cancer, but in some instances, the presence of blood is caused by hemorrhoids. In other cases, cancer might not be accompanied by blood in the stool.
The flexible sigmoidoscopy, which examines the bottom third of the colon, could miss a cancer farther up, The New England Journal of Medicine featured two large studies recently, which reported that the flexible sigmoidoscopy missed too many pre-cancerous growths in the sample of 5,000 patients.
Colorectal Cancer Facts
Colorectal cancer often shows no symptoms, which makes screening an important weapon in the fight against it. Regular screnings are important to catch the disease while it can still be cured. There are five different approaches to screening for colorectal cancer. Screenings should begin at age 50 for people with average risk factors. People with increased risk factors for colorectal cancer include those with a personal or family history of colorectal polyps; colorectal cancer; inflammatory bowel disease; or ovarian, endometrial or breast cancer.
Colorectal cancers grows slowly, early detection significantly increases survival. When detected early, the five-year survival rate is 90%. However, less than 40% of colorectal cancers are discovered at that stage. After the cancer has spread, the five-year survival rate drops to 65%.
Screening rates for colorectal cancer are dangerously low, and rates decrease as individuals age. Studies indicate that less than 40% of adults over the age of 50 have ever had a sigmoidoscopy. In addition, a recent GAO report indicates that even though Medicare coers colorectal screenings, the use of these tests remains dangerously low.
A 1997 study indicated that many primary care physicians do not appropriately screen patients for colorectal cancer because of concerns about the effectiveness of screening and misconceptions about patient's willingness to be screened. In addition, many patients are concerned that the screening exam might be unpleasant and are embarrassed to discuss the tests with their physicians.
Cancer that begins in the colon is called colon cancer, and cancer that begins in the rectum in called rectal cancer. Cancer affecting either of these organs may also be called colorectal cancer.
Questions and Answers with Dr. Senay
Q: Using a DNA sample is obviously less invasive than getting scoped. How does it work?
A: Researchers at the Mayo clinic took stool specimens from the participants in the study and analyzed it for DNA abnormalities that are unique to pre-cancerous polyps or early stage cancer of the colon or rectum. It's akin to the fecal blood test that's currently used to detect bleeding.
Q: Will DNA testing replace colonoscopies?
A: No, not right now. That's still the "gold standard," and I should point out that this test is about two years away from being widely available. Additional testing will get underway in January, but findings of this study are very exciting, and this technology could lead to much more patient-friendly way for early detection of colon cancer.
Q: The next method you mentioned is currently available. It's called a "virtual colonoscopy."
A: Yes, it's another non-invasive procedure that uses CT scanning technology. It can detect precancerous polyps and cancerous lesions as small as 6mm. The scan takes less than 30 seconds and provides a detailed look at the interior of the colon that's read by a radiologist.
Q: Is it as effective as a real colonoscopy?
A: For detecting polyps under 5mm, the real scope is better. But, polyps much larger than that can be cured. However, even in the best hands, the scope misses as much as 10% of pre-cancerous polyps. The people we spoke with at InsideTrac hope that the ease and lower cost of this procedure eventually leads to more frequent and therefore better screening. Colon and rectal cancers are usually slow growing, so if people over age 50 are getting screened every three years with this method instead of every five with a scope, it could be more effective.
Q: Colorectal cancer is very treatable but do we know the cause?
A: The exact causes are not known. Some studies have show that there are some risk factors that can increase a person's chances of developing it. Such as age, it's more likely to occur in those over 50. And, diets that are high in fat and calories and low in fiber. Family history is also a factor. Research shows women with a history of cancer of the ovary, uterus and breast have a higher risk of developing colorectal cancer.
Q: Screening is recommended for everyone over age 50. What are some common symptoms?
A: Yes, because it can be cured, it's important to recognize the symptoms. They are:
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