ESTES PARK, CO – , said gastroenterologist Swati G. Patel, MD, at a conference on internal medicine sponsored by the University of Colorado.
Bruce Jancin/MDedge News
Dr. Swati G. Patel
The startling rise in the incidence of colorectal cancer (CRC) in younger individuals in recent decades has generated much media coverage and considerable public concern. Reliable national data document a steady decline in CRC incidence over the past several decades in every age group 50 years and older – but a steady rise in incidence in those under age 50.
“The overall decline in CRC incidence and mortality beginning in the mid-1980s is an extremely amazing success story in cancer prevention. But there is still substantial work to be done,” observed Dr. Patel, who directs the Gastrointestinal Cancer Risk and Prevention Center at the university and is a staff physician at the Denver Veterans Affairs Medical Center.
Toward that end, in May 2018 the American Cancer Society issued updated guidelines recommending that people at average risk for CRC should now start undergoing regular screening for the disease at age 45. Models show that starting at age 45 rather than 50 would result in a 6.2% boost in life-years gained and a 17% increase in colonoscopies (CA Cancer J Clin. 2018 Jul;68(4):250-281).
“A different clinical and pathological entity”
Compared to CRC with onset at age 50 or later, early-onset disease is more often symptomatic at presentation. It is also significantly more likely to be located in the left colon or rectum, have a mucinous or signet ring histology, and be Stage III or IV.
“The disease seems to be a different clinical and pathological entity in younger patients,” Dr. Patel said.
The incidence of CRC before age 50 increased by 51% from 1994 to 2014. Mortality due to early-onset CRC rose by 11% during 2005-2015. Up to 90% of cases of early-onset CRC are diagnosed in individuals in their 40s. At the current rate of increase, early-onset CRC is projected to account for 20% of all cases of CRC by the year 2030.
The steadily rising incidence of early-onset CRC can’t be explained away as being due to earlier detection through greater availability of colonoscopy, in Dr. Patel’s view.
Numerous hypotheses have been put forth regarding the etiology of the rise in early-onset CRC. Correlations have variously been noted with the obesity epidemic, red meat consumption, diabetes, metabolic syndrome, increased early childhood exposure to antibiotics with resultant changes in gut microbiota in recent decades, and atopy.
“These are all fascinating hypotheses that will take decades to answer,” she said. “But in the meantime, what can we do about it now?”
Vital role for primary care
It’s going to take time to unravel the etiologies of early-onset CRC, both genetic and non-genetic. In the interim, opportunities abound for prevention and earlier detection. These opportunities are most available to primary care clinicians, since they provide continuity of care and are best positioned to detect red flags for patients at high risk for hereditary cancers.