A study led by my colleague Rebecca Siegel, MPH made headlines this week when it identified a worrisome rise in colorectal cancer (CRC) death rates in white adults under 55. The study, published in the Journal of the American Medical Association (JAMA), shows that in the mid-2000s, the death rate for colorectal cancer began to rise about 1 percent per year in white adults ages 20 to 54.
The numbers are not insignificant. In 2015, the latest year for which we have data, there were more than 6,600 colorectal cancer deaths in people younger than 55 in the US. That works out to 13 percent of all CRC deaths. Nearly 3,500 of those were in people under 50. For comparison, there were 4,175 total deaths from cervical cancer that year.
The reasons for this rise are as yet unknown, with various theories including antibiotic use that can affect what’s called the “microbiome,” the army of microbes in our bodies that protect us from germs, break down our food, etc.
Studies like this help define the questions that steer cancer control research, and eventually, cancer control efforts in the community. At a time when resources are scarce, these studies justify the questions that should be the focus of research.
One question that cropped up right away was: does this mean that colorectal cancer screening should start earlier? The answer is: not necessarily. Identifying a population at risk is only the first step. An equally important next step is answering the crucial question: Can screening make a difference?
The purpose of screening is simple: to prevent the most deaths without creating substantial harms. For decades, cancer control efforts have emphasized the potential of screening to catch cancer early, when it’s more treatable. Only recently has there been a concerted attempt to balance that message by noting that every screening test also has harms. Groups that make screening recommendations have to weigh the harms and benefits of a screening test and the treatment that comes as a result of screening.
The question now becomes: “Will widespread screening of younger people for colorectal cancer prevent enough deaths to offset the potential harms of additional screening?” The answer lies in:
1) Whether or not the biology of colorectal cancers in younger people is the same as the biology in older people, so that screening has a chance to be effective using the current tools, and;
2) Measuring how many will be harmed by screening.
Several studies suggest that younger people who develop colon cancer are more likely to develop cancers in the left side of the colon. Several studies also suggest that the presentation of colorectal cancers as a flat lesion versus a polyp differs by age. Flat lesions are more difficult to detect and remove with colonoscopy. Screening with a stool blood test might actually wind up being a better initial test for younger people.
Finally, studies suggest that younger people have faster growing cancers compared to older persons. This means the disease may move too quickly to be caught by regular screening, a key factor in whether routine screening works.
The definitive answer about screening people under 50 can only be obtained through a clinical trial to find out if routine screening of this population can reduce the risk of death. Such a trial would require years to get an answer. Population modeling may give us an earlier indication of the efficacy of screening without such a trial. The results of a modeling study are not as reliable as that of screening clinical trial, but they may be all we get.
Late in 2016, the American Cancer Society convened a group of experts to update its colorectal cancer guidelines. They are looking at all the colorectal cancer screening data in the US and Europe. They are looking at clinical and epidemiologic studies and handicapping them to determine which are the most trustworthy. They are also looking at mathematical population models. In the near future we expect them to make a new recommendation regarding colorectal cancer screening.
For now, there are a couple very important things we can do. Most importantly, we must work to make sure everyone at average risk begins colorectal cancer screening at age 50; not 53, not 55, not 60, but 50. The most recent survey shows that while screening is increasing, only 46 percent of people ages 50 to 54 were up-to-date compared to 67 percent of 55 and older. A substantial number of deaths from colorectal cancer could be prevented if we changed that number.
Second: we need to take symptoms of colorectal cancer in people under 50 seriously, and disavow the notion that it only affects people 50 and over. Symptoms to be aware of: changes in bowel habits, like constipation, diarrhea, or narrow stools; feeling that you still have to go after having a bowel movement; rectal bleeding; bloody stools; unexplained weight loss; abdominal discomfort, cramping, or pain; and weakness and fatigue.
The reality is we don’t know yet why this happening, even in the face of improved treatment for colorectal cancer. What we do know is that good research provides us with answers to questions, but also leads to more questions we need to answer.
Otis Webb Brawley, MD, MACP, FASCO, FACE is Chief Medical Officer of the American Cancer Society. He also serves as professor of hematology, oncology, medicine and epidemiology at Emory University. He is a Fellow of the American Society of Clinical Oncology, a Fellow of the American College of Epidemiology and one of less than 1400 physicians to be named a Master of the American College of Physicians in its history. In 2015, Dr. Brawley was elected to the National Academy of Medicine in recognition of his expertise in cancer control and cancer screening.