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Analysis of colorectal cancer (CRC) incidence by age in the U.S. revealed a spike right when screening is recommended to begin, indicating that many latent tumors go undiagnosed ahead of routine colonoscopy.

The incidence of CRC jumped by 46.1% from age 49 to 50, coinciding with the start of recommended screening, as compared to increases of 11.5% and 13.8% in the years prior, Jordan Karlitz, MD, of the Southeast Louisiana Veterans Health Care System in New Orleans, and colleagues reported.

And 92.9% of CRCs diagnosed at age 50 were cases of invasive disease, they wrote in .

"Early-onset colorectal cancer incidence rates have been increasing, so this is an important topic," Karlitz told 妖姬直播 by email.

In their study, the rate of local disease increased by 75.9% from age 49 to 50, while regional disease increased by 30.3%. The increase in the rate of distant disease was lower, at 15.7%, though was notably higher in black versus white patients (27.1% vs 13.9%).

Detection rates were the same at ages 51 and 52 as they were at age 50 -- at about 52 per 100,000 population.

As earlier-stage disease is detected with the introduction of screening, the estimated 5-year overall survival was worse for those diagnosed with CRC at age 49 (68.2%) compared with those diagnosed at age 50 (75.1%).

Karlitz pointed to past research suggesting that the average doubling times for CRC is , "which reinforces that many cancers detected at 50​ years were present for several years prior.​"

The current study joins a number of recent papers highlighting the rise in CRC incidence in younger patients, particularly those ages 45 to 49, Daniel Labow, MD, of the Icahn School of Medicine at Mount Sinai in New York City, told 妖姬直播.

"It is yet another example of the rise in colon cancer in this age group that is completely preventable by colonoscopy if caught as a polyp," said Labow, who was not involved in the study. "Though many will have normal colonoscopies at this age, and thus maybe 'unnecessary,' the fact is, if we prevent a cancer, we also prevent the cost of surgery, chemotherapy, time off of work, etc., etc. -- not to mention the emotional and physical toll it takes on the patient and family."

Labow noted that there has been building pressure to lower the recommend age for screening colonoscopy.

In 2018, the American Cancer Society changed its recommendations for CRC screening, and stated that average-risk individuals should begin screening at age 45.

But not everyone agrees with this shift. Guidelines released last year by the American College of Physicians, for example, still recommend starting at age 50 and more importantly, so do 2015 guidelines from the U.S. Preventive Services Task Force (USPSTF), which often determines whether insurance will cover preventive screening. (The Task Force updates its guidelines every five years.)

"The USPSTF should speak up and help push insurance companies to pay for the life-saving tests," said Labow.

Between ages 45-49 and 50-54, the incidence of CRC nearly doubles, according to Karlitz and colleagues. But the authors argued that these rates in the younger age group are not actually that low, as a large number of cases go undetected until screening at age 50 commences. It is estimated that more than 29,000 CRC cases could be prevented in the U.S. by starting screening at age 45, for a cost of $10.4 billion, which was .

"It is important to highlight that an undetected, preclinical cancer case burden may be present in patients of any age, including those over age 50, which may be compounded by non-optimized CRC screening rates," said Karlitz. "But a key aspect of our study is that we assessed this preclinical burden in those approaching screening age, which is important given ongoing debates on when screening should be initiated (45 vs 50)."

For their analysis, the researchers examined data on 165,160 individuals from the Surveillance, Epidemiology, and End Results (SEER) 18 registries who were diagnosed with CRC from 2000 to 2015. Among these, 56% were men, three-fourths were white, and 14.4% were black.

From age 49 to 50, the rate of CRC incidence rose from 34.9 to 51.0 per 100,000 population. The group estimated that in the "theoretical absence of screening," the increase from age 49 to 50 would have been 16.6%.

The observed increase was generally consistent across U.S. regions (ranging from 35.5% in the South to 56.0% in the Northeast), race/ethnicity (46.2% in whites, 47.3% in blacks), sex (52.9% for men, 39.1% for women), and tumor location (51.4% for colon and 37.6% for rectal cancers).

Given that the data are population-based, Karlitz noted that one limitation is the inability to "definitively determine" how long a CRC had been developing prior to being diagnosed.

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