By Will Boggs MD
NEW YORK (Reuters Health) - 24/5/2019
"Although the total number of young patients with CRC is still low, this dramatic increase in the last years warrants further research for causation and identification of patients at risk so measures can be taken in the (near) future to prevent CRC to occur or detect it at an early stage in these patients," Dr. Manon C. W. Spaander from Erasmus MC University Medical Center, in Rotterdam, the Netherlands, told Reuters Health by email.
Several groups in North America, Australia and China have reported increases in the incidence of CRC among individuals aged 20-40 years, and the American Cancer Society (ACS) recently recommended lowering the age to start CRC screening from 50 to 45 years.
In the first study, Dr. Spaander and colleagues used data from national and regional cancer registries from 20 European countries on more than 143 million people aged 20 to 49 years to evaluate age-related CRC incidence and mortality between 1990 and 2016.
CRC incidence rose from 0.8 to 2.3 cases per 100,000 persons among those aged 20-29 years, the team reports in Gut, online May 16.
Among people 30 to 39 years old, CRC incidence increased from 3.7 to 7.1 cases per 100,000 men between 1990 and 2016 and from 2.8 to 6.4 cases per 100,000 women between 2006 and 2016.
Among individuals aged 40 to 49 years, the incidence dropped between 1990 and 2004 but increased from 15.5 to 19.2 cases per 100,000 persons between 2005 and 2016. As for country-specific trends, the CRC incidence among individuals aged 20-39 years increased in 13 countries, did not change significantly in six countries, and decreased in one country (Italy).
Among those aged 40 to 49 years, CRC incidence increased in eight countries, did not change significantly in 11 countries and decreased only in the Czech Republic.
CRC mortality did not change significantly in the 20-29 years age group, but decreased 1.1% per year in the group aged 30 to 39 years, and in the group aged 40-49 years decreased 2.4% per year between 1990 and 2009 but increased 1.1% per year thereafter.
In the second study, Dr. Reinier G. S. Meester from Stanford University School of Medicine, in Stanford, California, and colleagues used data from the Surveillance, Epidemiology, and End Results (SEER) database to investigate trends in CRC incidence by stage in adults aged 40 through 49 years.
The incidence of CRC in this age group decreased from 1975 through 1995, but increased significantly thereafter through 2015, the researchers report in the May 21 issue of JAMA.
Average annual percentage changes over the last 20 years ranged from 1.3% for regional disease to 1.4% for localized disease to 2.9% for distant disease, which represented a statistically significant change in the overall stage distribution.
While the proportion of localized CRCs did not change significantly since 1995 and the proportion of regional CRCs decreased from 39.0% to 35.6% of CRCs, the proportion of distant CRCs increased significantly from 21.7% to 26.6%. This increase could not be explained by the drop from 5.5% to 4.0% in unstaged cases.
Dr. Meester told Reuters Health, "It is well documented that the incidence of colorectal cancer is increasing in younger adults, but the causes remain unclear. It has been suggested that early diagnosis due to screening in the ages 40-49 may be driving some of the trend. We wanted to test this hypothesis by looking at trends in incidence by stage. Although we knew that we might not find a shift towards earlier stage at diagnosis - only 15% of adults in this age group had a recent colonoscopy - we had not expected to find the exact opposite, that the disease is actually diagnosed at relatively later stages."
"These trends deserve ongoing attention from researchers and clinicians, both to better understand the causes and to reverse trends," he said. "At this point, one of the most cost-effective prevention methods may be the earlier adoption of screening, as recommended by the ACS."