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February 9, 2004

New Findings on Colorectal Cancer
By Thomas G. Dolan
Vol. 16 No. 3 p. 37

The good news about colorectal cancer is that there are protective health measures that can help protect against it, and early screening can virtually prevent it. The bad news is that by the time the symptoms appear, the cancer has been deeply embedded.

These are the findings of one of the most comprehensive studies to date on colorectal cancer (a term defining a number of cancers in the same area, such as anal, rectal, and colon cancer). The study, led by a team from the Veterans Affairs (VA) National Cancer Institute and Harvard University, appeared in the December 10, 2003, issue of The Journal of the American Medical Association. It included 3,121 veterans, aged 50 to 75, who were symptom-free and underwent complete colonoscopies between 1994 and 1997.

Lead investigator David A. Lieberman, MD, chief of gastroenterology at the Portland VA Medical Center and Oregon Health Sciences University, reports that more than one in 10 volunteers showed evidence of advanced tumor even though they had no history of colon trouble and no symptoms prior to the test. This statistic, coupled with the fact that colorectal cancer is the second-leading cause of cancer-related deaths in the United States, with approximately 150,000 new cases and 50,000 deaths in 2003, leads Lieberman to emphasize the importance of early screening.

The formation of polyps, not in itself necessarily cancerous, can be a precursor to cancer. The screening, or colonoscopy, Lieberman explains, also incorporates the removal of these benign polyps, thus preventing the possibility of cancer.

There are four stages to the cancer. The first stage involves the formation of what are called flat polyps, which are easy to miss. By the second stage, however, they are visible and can be removed. By the third stage, the cancer reaches the lymph system, and then it spreads throughout the body (stage four).

“Once you have symptoms such as rectal bleeding, weight loss, and pain, prevention is too late,” says Lieberman. “This shows the importance of early screening.”
As with many diseases in which people are recommended to submit to a screening, there has been some uncertainty as to the screening’s accuracy. In a July 2000 article in the New England Journal of Medicine, Lieberman’s team, based on the same set of data, made the case for colonoscopy over sigmoidoscopy as the primary screening tool for colorectal cancer. In that analysis, sigmoidoscopy—a less extensive but frequently used test that examines only the lower part of the colon—missed one-third of the serious lesions detected by colonoscopy.

Priscilla Savary, executive director, Colorectal Cancer Network, Silver Spring, Md., says that the fecal occult blood test has “given false positives and false negatives.” Savary adds, however, that there is a new test on the market—so new that many physicians are not aware of it. If a DNA stool test indicates positive for cancer, then the patient would undergo a colonoscopy. However, if the DNA test indicates negative, there would be no need for the colonoscopy.

This is significant because the DNA test, though prescribed by a doctor, can be taken by an individual at home. This would help alleviate the natural resistance many people have in going to a hospital for a colonoscopy, especially when there was no apparent need in terms of symptoms.

However, Priscilla’s sister, Joan Savary, a colorectal cancer survivor, says colonoscopies should not be feared. “The only real discomfort is the day before in which you eat nothing and take medications to clean your system,” she says. “For the colonoscopy itself, you’re given a mild sedative. A lot of people fall asleep. And for the vast majority, it’s painless.”

The standard medical recommendation is that screenings should start at the age of 50. However, both Savary sisters say they have “a different perspective”—the reason being that Joan contracted the cancer at the age of 44.

Priscilla says this type of cancer “occurs at any age. Children aged 2 to 4 are routinely checked, so thousands of polyps are removed. We’ve known of children 8 and 11 years old who have had a colon removed or died. And, once you’re over the age of 18, there is an increasing number who have it. One woman who had problems at the age of 18 was told that she had stress or an irritable bowel. She continued to have problems and was no longer willing to pass it off as stress, so she kept insisting to doctors that something was wrong until it was finally discovered that she had stage 3. Why wait until the age of 50 when there is a better than 90% chance of catching the polyps before cancer, and the survival rate for stage 4 is 7% to 9%?”

Priscilla recommends starting the testing at the age of 20 and alternating the DNA test with a colonoscopy every five years. “Now, 13 million people are screened every year at a cost of $10.4 billion for this disease. But, if you start at the age of 20, you screen only once every five years and can vastly reduce that cost. This is the only cancer that has the possibility of being close to 100% eliminated.”

Meanwhile, as Joan attests, the effects of therapy are “debilitating.” She adds, however, that the support group is a great comfort. “I think more people should get involved in support groups,” she says. “We have a face-to-face network support, as well as online support. Doctors can spend only so much time with you, and while we don’t give medical advice, we do try to explain what is happening and why; when they go back to their doctors, they will have formulated questions that will help them get the most out of their visit. I think it makes treatments go easier if you have a support group to fall back on.”

In looking at factors that increase the risk of colorectal cancer, the research poses yet another reason to quit smoking. Smoking increased by nearly twofold the risk of having a tumor or benign polyps, which often become cancerous. Having a close relative with colorectal cancer also elevated risk, but not as much as smoking. The consumption of red meat and alcohol were associated with a slightly higher risk. Body weight and cholesterol proved unrelated to cancer risks in this study.

There are several dietary factors that appear to play a protective role in preventing colorectal cancer. Doctors recommend a diet rich in fruits, vegetables, and fiber from whole grains and low in animal fat, especially from red meat. Nutrients that appear key in the cancer fight include calcium, vitamin D, folic acid, vitamin B, and antioxidants such as vitamin E and selenium.

Lieberman says his findings support current dietary guidelines for the prevention of colorectal cancer. “These data reaffirm relatively simple and safe recommendations that may reduce the risk of this cancer,” he says. “Stop smoking, reduce alcohol and red meat consumption, take a multivitamin, exercise regularly, and consume vitamin D, calcium, and cereal fiber.”

Another significant association with reduced risk was the use of nonsteroidal anti-inflammatory drugs. Men who took a daily aspirin were approximately two-thirds as likely to have a tumor. However, Lieberman cautions that further study is needed before recommending this tactic for protection against colon tumors because of the potential for side effects over a lifetime of anti-inflammatory consumption.

Though the general findings of the causes and preventive measures were along generally accepted lines, Lieberman says the sorting out of the relative importance of these nutrients was a challenge. For example, exercise and the consumption of calcium, folic acid, and multivitamins, though good for general purpose health, were shown to be marginally beneficial in lowering risk.

Perhaps the most significant finding in the study is the importance of vitamin D—the “sunshine vitamin”—in preventing colorectal cancer. “The finding that may surprise the scientific community is the vitamin D data,” says Lieberman. “Higher levels of vitamin D intake were associated with a lower risk of serious colon polyps. There have been some studies suggesting this, but our data are compelling.” In the study, men who consumed higher amounts of cereal fiber—more than 4 grams per day—and vitamin D—more than 645 international units per day—were significantly less likely to have the serious polyps or tumors, which are often the precursor to cancer.

Vitamin D was recognized in May 2002 when scientists demonstrated in an animal study that the nutrient works to prevent colon cancer by detoxifying the body’s own digestive products. But, vitamin D has generally been overshadowed as a colon cancer protector by calcium, which vitamin D helps the body use. In a 1999 study of 832 patients, calcium supplements had a modest protective effect against colorectal tumors. In Lieberman’s study, calcium alone showed only a minor beneficial effect.

Despite vitamin D’s many benefits, Lieberman cautions that it can be toxic in high amounts and cause nausea, constipation, weakness, and other symptoms. Yet, another problem is how to get enough of it. Cod liver oil is probably the best source—one tablespoon contains 1,360 international units. Milk is fortified with vitamin D, but with only 400 international units per quart. Liver and eel are other good sources, but you won’t find them on many dinner tables. Other fatty fish, such as salmon, mackerel, and sardines, are also good sources.

Perhaps the best source for the vitamin is sunlight. Exposure to sunlight triggers vitamin D production in the body, but researchers are unsure how this interacts with dietary intake to provide adequate levels for cancer protection. Lieberman says his findings should prompt research to determine how regular exposure to sunlight affects the risk of colon cancer.

It may be that when people used to regard sunlight as a totally benign force, they spent enough time in the sun to get plenty of vitamin D. However, health officials warn that sunbathers are putting themselves at greater risk of skin cancer. The use of sunblock creams and lotions protects against the sun’s rays but also blocks absorption of vitamin D.

Although Joan Savary was stricken at an early age, cancer is still associated more with older people. Here, the problem of vitamin D, or rather the lack thereof, dovetails with a general lack of that vitamin in older people. In her book Stop Aging Now! (Harper Collins, New York City), Jean Carper, a health authority who bases her findings on medical research, quotes Michael F. Holick, MD, PhD, an endocrinologist at Boston University Medical Center, as saying that older Americans suffer “a silent epidemic of vitamin D deficiency.” Vitamin D is needed to absorb calcium, but, according to Holick, up to 40% of older people who break their hips lack vitamin D mainly because aging skin is less able to make vitamin D from sunlight and aging kidneys are less able to convert the vitamin to the active type.

Carper says that if you are exposed to plenty of sunlight, 200 international units of vitamin D is probably enough, but older people who are rarely in the sun require 600 international units—close to Lieberman’s recommended dose of more than 675 international units. However, Carper points out that research indicates that consuming more than 2,000 international units could be toxic. Most experts recommend not to exceed 2,000 international units.

In other words, the daily multivitamin providing 200 international units is not enough, and most people—especially older people who don’t get out in the sun much—are not going to have the eating habits to make up the difference. On the other hand, just two tablespoons of cod liver oil can put you in the toxic range. This would seem to indicate some careful thinking, but the solution is actually not too difficult. A multivitamin and one or perhaps two teaspoonfuls (at approximately 500 international units per teaspoon) of cod liver oil per day should maximize vitamin D intake without the toxic danger.

Of course, taking the right vitamins is all well and good, but Priscilla Savary has another perspective. She’s all for avoiding the risks and eating right, but she points out that “in studies on diet and health, it’s very difficult to pinpoint things conclusively. The risk factors supply only 20% of those who actually get colorectal cancer. Some people smoke their whole lives and never get this cancer. On the other hand, we know of a perfect athlete who bowled, golfed, ran, wasn’t overweight, drank only water, and did not have it in his family and still caught this cancer.”

The best solution? “Early screening and do everything else in moderation,” she says, “except for laughing and dancing. Do as much of those as you can.”

— Thomas G. Dolan is a medical/business writer based in the Pacific Northwest.

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