Rafael Marcos Gragera
Epidemiologist at the Catalan Institute of Oncology and professor of medicine at the University of Girona
Both studies show an increase in the incidence of colorectal cancer in young adults in the United States and establish an ecological correlation with the decrease in the recommended age for initiating screening, which fell from 50 to 45 years. This expansion in the age range has allowed for the detection of asymptomatic cancers in people between 45 and 49 years of age, who previously did not undergo screening. This increase in diagnoses is mainly concentrated in local-stage tumors, that is, in early stages and with a better prognosis, suggesting a direct effect of earlier screening.
The editorial shows that mailing simple tests (such as the FIT test) significantly increases the participation of young people in screening programs. Furthermore, this has not negatively affected the participation of older adults, allaying one of the main fears that existed.
As the authors comment, potential limitations include the lack of individual-level information on colonoscopy use and the potential impact of the pandemic, in addition to having only four years of data after the initial screening recommendation.
A recent study on colorectal cancer incidence in Spain, led by Dr. Galceran and based on data from population-based registries, was recently published in the journal Clinical and Translational Oncology. The period analyzed spans from 1993 to 2016.
The main results indicate that no overall increase in colorectal cancer incidence is observed in the 20-49 age group. However, when broken down by more specific age subgroups, a significant increase in incidence was identified among men aged 20 to 29 years starting in 2006 (with an annual increase of 10.05%) and among women in the same age group throughout the period 1993-2016 (with an annual increase of 4.90%). In Spain, the target population for population-based colorectal cancer screening continues to be those aged 50 to 69 years, so the increase observed in young adults cannot be attributed to a screening effect. The most plausible hypotheses point to environmental and lifestyle factors, such as the adoption of a Western diet, increased obesity, sedentary lifestyle, and the increasing use of antibiotics, especially during early life. Among these factors, the rising prevalence of obesity is considered one of the most cited causes of the increased incidence in young adults. Other potential risk factors include alcohol consumption, processed meat consumption, and inflammatory bowel diseases.
The aforementioned article concludes that more prospective cohort studies are needed to better understand the causes of the increased incidence of colorectal cancer in young adults and its interactions with the environment, the microbiome, and the host.
The main recommendations derived from these studies include the need to increase public awareness about the importance of participating in colorectal cancer screening programs. In Spain, participation in these organized programs remains low, hovering around 40%, well below the desirable threshold for achieving a significant population impact. Furthermore, it is recommended to promote healthy lifestyles, which involves reducing sedentary lifestyles, combating obesity, and promoting a balanced diet, moving away from unhealthy dietary patterns that could be contributing to the increased incidence in young adults.