By Scott Baltic
NEW YORK (Reuters Health) - 9/7/2019
The incidence of colorectal cancer is increasing among European adults aged 20-49 years, broadly in parallel with trends already documented in 20- to 40-year-olds in North America, Australia and China, according to new findings.
Drawing from databases in 20 European countries, the study, online May 16 in Gut, found that the fastest rise in colorectal cancer (CRC) incidence was in the youngest (20-29) age group. Across age groups, the increase was sharper for colon cancer than for rectal cancer.
Despite these increases, there was no proportionate increase in mortality.
"The reason why there is an increase in CRC incidence in young adults over the last years is still unknown," said senior author Dr. Manon C. W. Spaander of the University Medical Centre Rotterdam, in Rotterdam, the Netherlands.
For adults generally, she told Reuters Health by email, obesity and little physical activity may play a role, but it isn't yet known whether this is also the case for younger adults who develop CRC.
If the increasing trend continues, Dr. Spaander's team suggests, screening guidelines may need to be reconsidered. In the meantime, clinicians need to be aware of the increase, the researchers note.
CRC-incidence data were available from 20 European nations, and mortality data were available from 16. Among the total 2009 population of the 20 countries, 143.7 million people were 20 to 49 years of age.
Of those, 0.13% were diagnosed with CRC from 1990 to 2016, 47,364 ages 20 to 39 and 140,554 ages 40 to 49.
In the age 20-29 group, CRC incidence rose from 0.8 cases per 100,000 individuals per year to 2.3. The average increase was 1.7% per year between 1990 and 2004, and 7.9% per year between 2004 and 2016.
Among 30- to 39-year olds, CRC incidence increased, though less sharply than in the youngest age group: For both sexes between 2006 and 2016, the incidence of colon cancer rose 6.4% per year, while that of rectal cancer rose 1.6% per year.
In the age 40-49 group, CRC incidence decreased by 0.8% between 1990 and 2004, but then rose by 1.6% per year from 2004 to 2016. A similar trend was seen for colon cancer specifically, but not for rectal cancer.
The CRC mortality rate did not change significantly in the 20-29 age group. Among those ages 30-39, CRC mortality decreased by 1.1% per year, but no significant change in mortality was seen regarding rectal cancer.
Among those 40-49 years old, CRC mortality decreased by 2.4% per year between 1990 and 2009, but then increased by 1.1% per year between 2009 and 2016.
Between-country differences were stark. CRC incidence in adults 20-39 increased significantly in 12 countries, but not in the rest, and Italy even showed a decrease.
Rebecca Siegel, scientific director for surveillance research at the American Cancer Society, in Atlanta, told Reuters Health by email that the between-nation differences in Europe are consistent with between-state differences in the United States. She noted that in some countries, such as the Netherlands, CRC incidence is increasing overall, "so it is not as surprising that rates in young adults are increasing."
The sharp contrast in the United States between a falling overall incidence of CRC and "somewhat rapid increases in younger adults," Siegel said, suggests "changes in exposure in early life that are altering risk of CRC."
Dr. Maria Ignez Braghiroli of the Centro de Oncologia, Hospital Sírio-Libanes, in Sao Paulo, Brazil, said that while overall CRC incidence is trending differently worldwide, in adults under age 45, "a global increase in new cases has been uniformly observed."
Regarding when to start CRC screening, Dr. Braghiroli told Reuters Health by email, some countries have reduced the recommended initial screening age to 45, yet economic and logistic difficulties remain in many countries. In any case, the population with the most-increased incidence seems to be younger than 45, and the total number of cases is probably too low to justify such a change, she said.
Dr. Braghiroli emphasized that it's nonetheless imperative to make physicians who are in contact with these younger patients aware of these findings, so they can investigate any worrisome symptoms earlier and make appropriate diagnoses sooner.