Not too young for colon cancer

Published - August 27, 2017 12:02 am IST

When researchers reported earlier this year that colorectal cancer rates were rising in adults as young as in their 20s and 30s, some scientists were sceptical. The spike in figures, they suggested, might not reflect a real increase in disease incidence but earlier detection, which can be a good thing. Now a sobering new study has found that younger Americans aren’t just getting cancer diagnoses earlier. They are dying of colorectal cancer at slightly higher rates than in previous decades, and no one really knows why.

“This is real,” said Rebecca L. Siegel, an epidemiologist with the American Cancer Society and the lead author of the current study, published as a research letter in JAMA , as well as of the earlier report. “It’s a small increase, and it is a trend that emerged only in the past decade, but I don’t think it’s a blip. The burden of disease is shifting to younger people.”

The study found that even though the risk of dying from colon and rectal cancers has been declining in the population overall, death rates among adults from ages 20 to 54 had increased slightly, to 4.3 deaths per 100,000 people in 2014, up from 3.9 per 100,000 in 2004. “This is not merely a phenomenon of picking up more small cancers,” said Dr. Thomas Weber, who was not involved in the study but is a member of the steering committee of the National Colorectal Cancer Roundtable. “There is something else going on that’s truly important.”

No one knows what underlying lifestyle, environmental or genetic factors may be driving the rise in cases.

While rates of cancers tied to human papillomavirus, or HPV, have been rising in recent years, that virus causes cancers mainly of the cervix, back of the throat and anus, and scientists do not believe sexual behaviours or HPV are driving the increase in colon or rectal cancer (anal and rectal cancers are distinct).

Diet, antibiotics possible factors

Obesity, a diet high in red or processed meats and lack of physical activity are among the factors tied to increased risk, but new research is looking at other possible causes. One recent study found, for example, that prolonged use of antibiotics during adulthood was associated with a greater risk of developing precancerous polyps, possibly because antibiotics can alter the make-up of the gut microbiome.

Scientists are also exploring whether the colorectal cancers emerging in younger adults are different from those seen in older people — and whether they can be detected and treated with the same tools. There is some evidence that young people are more likely to have precancerous polyps that are harder to see and remove during a colonoscopy because of their location in the colon or because they are flat rather than tubular, according to Dr. Otis Brawley, who is chief medical officer for the American Cancer Society.

The findings add to the urgency to find reliable ways to detect colorectal cancer early in young people. Most medical groups have for years recommended people start routine screening only at age 50 unless they have specific risk factors, like a family history of the disease or chronic conditions like inflammatory bowel disease that raise the risk. One organisation, the American College of Gastroenterology, recommends that African-Americans start routine screening at 45 because they are at higher risk for colorectal cancer than whites.

Any proposal to expand universal screening, however, will be both controversial and potentially costly, since the vast majority of colorectal cancer deaths still occur among older adults.

“I don’t know that this very small uptick in mortality means we ought to start doing colonoscopies on 20-year-olds as a routine matter,” said Dr. Michael Potter, a professor of family and community medicine at the University of California, San Francisco. More lives would be saved by increasing screening at age 50, he said, adding, “It’s worth doing research in this area to determine whether lowering the age of colorectal cancer screening would yield more benefits than harms. These are not risk-free procedures.”

Screening tests are also expensive, though cost is not the driving issue. Looking for colon cancer in young people is like looking for a needle in a haystack — you’d have to screen a lot of people to detect even a small number of cancers or precancerous polyps. Most young people would go through the process for no good reason, and some would sustain injuries or other harms.

Complications from colonoscopy, considered the gold-standard test, are fairly frequent. A study of over 300,000 healthy Medicare patients who had colonoscopies found that nearly 2% wound up in an emergency room or hospital within a week of the procedure because of complications such as tears in the wall of the colon or rectum, which can be life-threatening.

While some organisations specifically state that colonoscopy is the preferred screening method, the U.S. Preventive Services Task Force endorses a variety of screening tests, including some that are less expensive or non-invasive, though they may not be as effective in finding and preventing cancers. Stool tests that examine faecal samples for microscopic amounts of blood and DNA changes, for example, can indicate the presence of a tumour or polyp, but such tests need to be done more frequently and may have to be followed up with a colonoscopy if the result is positive.

All of the testing options have pros and cons, and some may yield a false positive test, subjecting someone to additional testing for no reason, or a falsely reassuring negative result.

But Dr. Brawley said there is good scientific data to show that stool sample tests save lives, and added that some patients may be better served by these noninvasive tests. “In the U.S., we have all gravitated toward the new high-tech screening methods, and we may be leaving old technology that is still very good,” he said.

Screening guidelines aside, people concerned about colorectal cancer at any age should talk to their doctor, said Dr. Douglas Owens, vice chairman of the Preventive Services Task Force. “There are always circumstances in which individual decision making is appropriate,” he said.

Many physicians may be reluctant to order screening tests for younger adults, because they are also unaccustomed to seeing this cancer in younger people, Weber said. He said efforts are being made to raise awareness in physicians as well as patients, adding, “We need to set the trigger much lower to investigate these symptoms and rule out malignancy.”

Warning signs of colorectal cancer include rectal bleeding, bloody stools, unexplained weight loss, fatigue and digestive complaints, or persistent changes in bathroom behaviour. Anaemia in men is also a warning sign and should be explored further, and while many doctors typically attribute anaemia in a premenopausal woman to menstruation, experts say that if a woman is experiencing any other symptoms, doctors should assess her for colon cancer. Make sure you know your family’s medical history — including not only whether any close relatives had colorectal cancer, but whether they had benign polyps, which can be precancerous. Tell your physician of any medical conditions, such as inflammatory bowel disease, that may increase your risk. Doctors say you may be able to reduce your risk of colorectal cancer if you maintain a healthy weight, get a lot of physical activity, eat a healthy diet, don’t smoke and avoid excessive use of alcohol. NYT

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