Incidences of invasive colorectal cancer (CRC) in patients aged 49 to 50 years are consistent with incidences of previously undetected CRCs diagnosed via screening at age 50 years, according to study results published in JAMA Network Open.

Rates of early-onset CRC are increasing; however, controversy surrounds whether screening should begin at age 45 or 50 years. Many cases of CRC do not produce symptoms; therefore, observed incidence rates of early-onset CRC in the Surveillance, Epidemiology, and End Results (SEER) registries do not reflect the burden of undiagnosed CRCs in patients younger than age 50 years. The objective of this study was to assess the incidence rates of CRC in 1-year age increments, focusing on the transition between the ages of 49 and 50 years.

In this study, researchers analyzed data from the SEER 18 registries for years 2000 through 2015, when rates of early-onset CRC started increasing and screening became more commonplace. They calculated incidence rates of CRC in 1-year age increments at every age from 30 to 60 years and stratified data according to US region, sex, race, disease stage, and tumor location. Investigators analyzed a total of 170,434 cases of CRC among 165,160 patients (55.9% men, 75.4% white and 14.3% black, with a mean age of 51.6±6.7 years).


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Results revealed steep increases in the incidence of CRC from 49 to 50 years of age in all SEER 18 registries (46.1% increase: 34.9 [95% CI, 34.1-35.8] to 51 [95% CI, 50-52.1] per 100,000 population) during the 1-year age transition. Steep increases from 49 to 50 years of age were also observed in all US regions, both sexes, white and black populations, and in both colon and rectal cancers. At 50 years of age, 8799 (92.9%) of the 9474 cases of CRC diagnosed from 2000 through 2015 were invasive.

This study had several limitations. First, researchers could not confirm that steep increases in the incidence of CRC from 49 to 50 years of age resulted from the increased detection of potentially asymptomatic preclinical CRCs. Second, researchers could not determine when CRC began growing in patients before the age of 50 years. Last, SEER 18 represents only 28% of the US population.

The study researchers concluded that steep increases in the incidence of invasive CRC between 49 and 50 years of age are consistent with a high burden of preclinical CRCs before screening at the age of 50 years. Moreover, relying on SEER incidence rates to estimate CRC outcomes in younger populations may underestimate the benefits of cancer prevention.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

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Reference

Abualkhair WH, Zhou M, Ahnen D, Yu Q, Wu XC, Karlitz JJ. Trends in incidence of early-onset colorectal cancer in the United States among those approaching screening age. JAMA Netw Open. 2020;3(1):e1920407.