Ward off colon cancer
Colonoscopy best way to prevent cancer
The Bulletin - February 15, 2007
By Markian Hawryluk
Of all the standard preventive health measures and screening tests, there may be no procedure that elicits as much fear and trepidation as the colonoscopy. There also may be no easier way to protect your long-term health.
"Colon cancer is arguably the most preventable cause of cancer deaths, and yet it's the second leading cause of cancer deaths in both men and women in this country," says Dr. Arthur Cantor, a gastroenterologist with Bend Memorial Clinic.
The American Cancer Society recently reported that deaths from the big four - lung, breast, prostate and colorectal cancers - dropped for the second year in a row, with colon cancer showing the most dramatic decrease. More than 2,200 fewer Americans died of colon cancer in 2004, the latest year for which statistics were available, than in the previous year. Those gains were attributed almost entirely to more widespread screening.
The impact of screening was confirmed in a recent study from Yale University that looked at colorectal cancer rates after Medicare initiated a screening benefit. Medicare began limited coverage of colon cancer screening in 1998 and moved to universal coverage in 2001. The number of screening colonoscopies tripled after 1998 and rose 6.5 times after 2001.
The researchers found that with each step, the number of cancers caught at an early stage increased, from 22.5 percent prior to 1998, to 25.5 percent in the interim years, and to 26.3 percent after 2001.
That progress clearly showed that screening could save lives. Colorectal cancer caught in the first stage has a 90 percent five-year survival rate.
Stage 2 colon cancer patients live for five years only 70 percent of the time, and Stage 3 patients only 50 percent. By the time the cancer has spread to other organs, Stage 4, the five-year survival rate is less than 30 percent.
Regular screening, however, can catch pre-cancerous growths before they become dangerous. With such a profound potential to save lives, in 2002, the U.S Preventive Services Task Force upgraded its call for colorectal screening from "simply recommending" to "strongly recommending" that all Americans over the age of 50 get screened. Still, despite the fact that both public and private insurers for the most part will cover regular screening colonoscopies, only about half of Americans over 50 have ever been screened.
As a result, some 52,000 Americans will die from colorectal cancer this year. The vast majority of those deaths would have been preventable with timely screening.
"Early-stage rectal cancers are much less often found than late-stage cancers, and that's strictly a screening issue," says Dr. Stephen Archer, a surgeon with Advanced Specialty Care in Bend. "If we can convince patients that it's painless and safe to have colonoscopies, then we're hoping that more patients will undergo colonoscopy because it helps prevent dying."
Early warning system
Colorectal cancer starts as a polyp, a growth on the lining of the colon or rectum. Some polyps will grow harmlessly, but others can develop into cancer within a decade. But in the early stage, they're easily removed during a colonoscopy.
A colonoscopy involves snaking an endoscope, a camera on the end of a flexible tube, through the colon to look for polyps. When the doctor finds one, he or she can extend a wire lasso around the base of the polyp, pull the lasso tight and burn off the polyp. It can then be sucked out with the scope.
In a full colonoscopy, the scope runs through about 5 feet of the colon, making two left turns along the way. Negotiating those turns can be tricky, particularly if the scope catches on the colon and the tube creates a loop rather than pushing the camera farther along.
"We inflate the colon with air, and when our bowels get dilated, they hurt," Archer says. "So that's what really hurts the most. That and the two big corners."
A traditional colonoscopy will find a polyp in about one in four men and in about one in six women. One to 2 percent of colonoscopies will identify a cancer.
But there are few indicators that can suggest who is at risk for developing colon cancer. About 20 percent of colorectal cancers occur in those at high risk for the disease, including those with a family history of colorectal cancer or polyps in a first-degree relative. Most cases occur in people at average risk for the disease, a group that includes all people over the age of 50.
While a handful of tests are available that can potentially identify colon cancer, the colonoscopy is considered the gold standard. But it's not perfect. Studies suggest that a traditional colonoscopy will miss up to 6 percent of polyps.
"Colonoscopy doesn't visualize well the back side of the folds of the colon," Cantor says.
It's a bit like driving a car without rearview mirrors. You can read the road signs ahead of you, but there's no way to read the signs on the other side of the road. There is a minimal risk of complications as well, such as perforation of the colon, affecting at worst, one in 1,000 cases.
With patients reticent to undergo colonoscopy screenings, doctors have looked for other less invasive ways to look for polyps and cancer. A fecal occult blood test, which requires only a stool sample, is an easy test to perform, but it is much less accurate at finding problems.
Virtual world
In recent years, doctors have turned to imaging equipment to take essentially an X-ray of the colon. Virtual colonoscopy relies on computerized tomography, also known as a CAT scan, or magnetic resonance imaging, known as MRI, to take thousands of pictures of the colon. A computer then uses sophisticated software to reconstruct three-dimensional image of the colon. The doctor can then conduct a fly-through of this 3-D model, offering the same view as a physician would see with an endoscope in a traditional colonoscopy. But unlike a traditional colonoscopy, because the image is computer generated, the doctor can look from many different angles.
"Theoretically you can see all surfaces," Cantor says. "So the blind spots which you can miss with an optical colonoscopy, you're not necessarily going to miss."
But studies comparing the efficacy of virtual colonoscopy have been mixed. Imaging technology is now nearly as good as an optical colonoscopy in picking up the larger polyps but can miss more of the smaller growths.
Traditional colonoscopy has the added advantage of being able to remove polyps at the same time. If a virtual colonoscopy identifies any area of concern, the patient must then undergo a traditional colonoscopy to remove it. That means doctors must also decide how big a polyp is to consider a problem worthy of following up. The bigger the polyp, the higher the likelihood that it will turn cancerous. Currently, most doctors use a 5 or 6 millimeter diameter as the cutoff.
"Right now, nobody knows for sure what size polyp requires a follow-up colonoscopy," Cantor says. "If you look at the studies, 1 percent of polyps less than 5 millimeters will (show signs of cancer). It's not totally safe. If I see that doing an optical colonoscopy, I just take that off without worrying about it. I take off everything I see."
Cantor says about 15 percent of people undergoing virtual colonoscopy will have a polyp bigger than 6 millimeters and will have to undergo a traditional colonoscopy to remove it. Virtual colonoscopies are also less adept at identifying flat polyps, which constitute about 20 percent of all polyps. And these polyps are more likely to develop into cancer.
Screening involving imaging technology does offer a fringe benefit. In about 14 percent of cases, a virtual colonoscopy will identify areas of concern outside of the colon, such as cancer in another part of the body or a calcium deposit that may signal heart problems. But Cantor says those may or may not turn out to be problems.
"One common scenario is we pick up a kidney cancer at an early stage. So somebody gets saved whereas they would never know about it," he says. "Then there are other circumstances where you pick up something that's totally incidental and then you end up doing a wild-goose chase for something that was never significant."
A virtual colonoscopy also costs less, around $700, compared with more than $1,000 for a traditional colonoscopy. Those costs can climb if performed in a hospital rather than in an office setting.
Insurance companies for the most part will pay for a standard colonoscopy but not for a virtual colonoscopy. Medicare will pay for a virtual colonoscopy only if a traditional colonoscopy failed to make its way through the colon. There are some insurers who won't pay for screening colonoscopies of any type without other signs suggesting a problem. So if a patient is footing the entire bill for the procedure, a virtual colonoscopy can be a cheaper option.
CAT scans also involve some radiation exposure. "It's not terrible, but it can be significant especially if you're going to do these studies repeatedly over time," Cantor says. While patients may like the idea of a noninvasive test, doctors say virtual colonoscopies don't avoid the worst part of the procedure. The patient must still clean out the bowel ahead of time and have his or her colon dilated with air.
"People complain about that," Cantor says. "A lot of people would prefer an optical colonoscopy. It's more comfortable because you get sedated."
Archer agrees.
"The hardest part of the colonoscopy is often the bowel prep. And no one has found an easy way around that," Archer says. "No matter what you do, you still have to get the colon cleaned out."
Researchers are working on a way to do a "virtual prep" for a virtual colonoscopy. It would involve drinking a solution a day or two before the procedure that would allow the computer to differentiate between stool and the colon. But that may be years away from being a reality.
Easing discomfort
Doctors are also finding new ways to make traditional colonoscopy less uncomfortable for the patient.
"We're using a drug that anesthesiologists use called propofol," Archer says. "It's a very effective drug. Patients have really good anesthesia; they don't feel any pain. And they don't have any memory of the procedure."
In the past, physicians performing colonoscopies in their office had to rely on narcotics to sedate the patient. However, those narcotics left patients groggy for the most of the day. Propofol is administered intravenously, so it takes effect more quickly and wears off just as fast. And it provides a deeper sedation than with narcotics.
Archer recently used propofol when undergoing his own colonoscopy.
"It was the kind of deal where they say, "We'll see you later,' and then you blank out," he says. "You wake a few minutes later and you wonder when they're going to start."
He had no idea the procedure was done. Ramona Hidalgo, a 39-year-old Redmond resident, has had endoscopy done with both the narcotic and with propofol. She says the biggest difference for her was in the recovery time.
"Once I woke up, the recovery was really quick," she says. "I still had to have someone drive me home, but I was still able to function. I could cook dinner for my family. I wasn't just wiped." That has tremendous appeal for patients and doctors alike, but not everybody is happy that the sedative is now being used in office settings.
"Up until now, if you wanted to get propofol, you had to go to a hospital to get it and have an anesthesiologist give it," Archer says. But that adds to the cost of the procedure. And many insurance companies balked at paying for an anesthesiologist when colonoscopies could be done without one.
It has also pitted doctors against anesthesiologists in a turf war over sedation. Some doctors have trained nurses to administer the drug under their supervision. A majority of state nursing boards, including Oregon's, do not expressly ban nurses from serving in that capacity.
But anesthesiologists have countered that using propofol can be risky if someone is not trained in anesthesia and have pushed regulators to require an anesthesiologist to be on hand when propofol is administered. Advanced Specialty Care has hired several nurses trained in the use of propofol to bring the option to Central Oregon. Rosie Donelly, a registered nurse who oversees the program for the practice, says she's seen the impact the drug has on patients.
"To me, it's night and day," she says. "Most patients don't remember the procedure at all. Most wake up and ask, 'What are you doing in my room?'"
Advanced Specialty has now performed more than 417 procedures using propofol without any complications. Physicians are hoping that options such as propofol and virtual colonoscopies might encourage people who have never been screened to get over their fears and discomfort.
"What doctors are trying to do is make it as appealing as possible," Archer says.
Cantor believes that most of the patients who have come to the clinic for a virtual colonoscopy probably would never undergo a traditional colonoscopy. So it may be a way to screen more people.
"My guess is virtual colonoscopy is never going to catch on in a big way," he says. "It might be something that some people use, but it won't be something that everybody gets."
Researchers are trying to develop even less invasive screening methods, such as the use of DNA testing to find cancer or polyps in the stool or a blood test that would find markers of colon cancer in the blood, similar to the way prostate cancer can be identified through a prostate-specific antigen test known as a PSA. In the meantime, doctors hope patients will undergo a little discomfort to gain a lot of health benefit.
"The important message is that screening saves lives and that any screening method is better than none," says Dr. Mark Pochapin, director of the Jay Monahan Center for Gastrointestinal Health and spokesman for the American Society for Gastrointestinal Endoscopy. "The message is simple: If you are over 50 or have a family history of colorectal cancer, talk to your doctor about getting screened today."
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The Bulletin
Markian Hawryluk: (541) 617-7814
mhawryluk@bendbulletin.com
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