Rise Seen in Colorectal Cancer in Under-50 Adults

June 8 (Bloomberg) — Colorectal cancer rates are rising in adults younger than 50 with the biggest jump, more than 5 percent, recorded in those ages 20 to 29, a study found.

People older than age 50 began getting tested routinely for the disease in the mid-1980s, leading to a 2.8 percent yearly decline from 1998 to 2005 in adult men overall, according to the American Cancer Society report. Younger Americans, who make up 9 percent of the 146,970 cases expected by the society this year, aren’t usually tested for the disease, the second most common cause of cancer death in U.S. adults.

The study was published today in the journal Cancer Epidemiology Biomarkers and Prevention. The research didn’t identify a cause for the increase. Elizabeth Ward, vice president of surveillance and health policy research at the society, said rising obesity and diabetes rates and diets heavy in red and processed meats are likely culprits.

“The fact that cancer is affecting younger people is worrisome,” said Ward, a study author, in a telephone interview. “We want to educate health-care practitioners and the public that this increase is happening, and it may be related to obesity and unfavorable dietary patterns.”

From 1992 through 2005, the rate of colorectal tumors climbed 1.5 percent a year in men ages 20 to 49 and 1.6 percent a year in women the same ages, the study found. The increase was seen largely on the left side of the colon and rectum, sites where red meat consumption is a risk factor, the report said.

Younger Adult Symptoms

The study should raise vigilance about symptoms reported in younger adults, including rectal bleeding, abdominal pain, changes in bowel habits and anemia with blood in the stool, the researchers wrote. Early cancer detected by screening often doesn’t have symptoms, so by the time doctors detected cases in the younger adults, the cancers were invasive, the report said.

The report didn’t have a national count of cases in each age group. The percentages in the study represent a projection of rising national rates based on a sampling of cases diagnosed in people ages 20 to 49 from 1992 to 2005, rather than from the total number of cases, the authors said. The data were drawn from federal cancer registries.

Colorectal malignancy is expected to cause 49,920 deaths overall in 2009, the society said. This is the first study to take a comprehensive look at this cancer’s increase in younger adults. Rates and case counts before 1998 weren’t included in the study, said spokesman David Sampson.

Tobacco, Alcohol

While tobacco and alcohol are potential risk factors for colorectal cancer, the researchers said they are unlikely to explain the rate increase because alcohol intake has edged down since 1981, and tobacco use takes at least 30 years to lead to colon cancer, the study said.

“I was alarmed reading this. I had no idea this was happening,” said Peter Gann, a physician and cancer epidemiologist at the University of Illinois at Chicago College of Medicine in a telephone interview. “The big news has been the decline in incidence. Of course, this is a population that is not screened so it wouldn’t be affected by screening.”

Gann, who wasn’t involved in the research, questioned whether there may also be a link with increases in anal cancers driven by human papillomavirus (HPV), a sexually transmitted infection that raises cancer risk.

The American Cancer Society, based in Atlanta, has recommended since the 1980s that adults age 50 and older get routine screening for colorectal cancer.

Recommendations

“For people younger than 50 we don’t recommend routine screening at this point,” said Ward in an interview, “because the rate isn’t high enough that the benefit exceeds the risks.” Testing of people under 50 is advised if they have genetic risk factors, a family history of the tumors or inflammatory bowel disease that raise their odds of malignancy, she said.

Before any policy changes can be made to address the rising cases, the trend should be confirmed by other researchers, said Sampson of the cancer society. Next, the study urged scientists to probe lifestyle and environmental triggers for the increase, and to search for ways to prevent it.

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