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We read with interest the article titled ‘Increasing incidence of colorectal cancer in young adults in Europe over the last 25 years’ by Vuik et al, in which they analysed trends in colorectal cancer (CRC) among young adults (20–49 years old) and found that CRC incidence is increasing among young adults in Europe.1 We have found that the incidence of CRC in young adults in Europe is significantly different from that in the USA.2 Therefore, we analysed the incidence of CRC in young adults with data from the Surveillance, Epidemiology and End Results database (from 1990 to 2016, a total of 78 295 cases, aged from 20 to 49 years) by the Joinpoint regression method and compared it with the results from Europe.
We found that the incidence of CRC in young adults in the USA increased annually, with an annual per cent change (APC) of 4.3% in the age group of 20–29 years, 2.47% in the age group of 30–39 years and 1.8% in the age group of 40–49 years (figure 1A–C). Although the incidence rate was increasing, the mortality rate had not changed significantly, which may be related to young adults presenting with more local or regional disease.3–5 We know little about the indications for colonoscopy in young adults, but studies have shown increases in colonoscopy use that parallel the incidence of CRC in young adults, which could explain the increasing rates of local or regional disease.4 Conversely, some studies reported that CRC in young adults was more aggressive and resulted in worse survival, perhaps because they had more mucinous and signet ring cell histology, had a family history of CRC and were less likely to be screened.6 In addition, we found that while the incidence of CRC in Europe was also increasing in young adults, the rate of increase in the USA was significantly higher than that in Europe (figure 1A–C). This may be because the USA has a significantly higher incidence of obesity than Europe. In 2012, the obesity rate in the USA was 35%, and it was as high as 39.8% in 2016; however, in Europe, the obesity rate was approximately 15.9% in 2014.7 Next, we observed that the APC in the USA ranged from 3.0% (1990–2011) to 16.0% (2011–2016) in the age group of 20–29 years (figure 1D), and from 1.5% (1990–2013) to 10.3% (2013–2016) in the age group of 30–39 yearss (figure 1E). The trend in the incidence of CRC in patients aged 20–39 years became steeper in 2011–2013. This may be related to the US government’s implementation of the Affordable Care Act in 2010, after which the proportion of adults aged 19–34 years who were uninsured reduced from 28% in 2013 to 18% in 2016.8 The incidence of CRC in both the USA and Europe is growing the fastest in the age group of 20–29 years and the slowest in the age group of 40–49 years (figure 1A–C). This is likely because the incidence of CRC in young adults is closely related to family history.9 The incidence rate of rectal cancer in the age group of 40–49 years in Europe is stable (figure 1I), which may be related to antibiotic use, periodontal disease and pH levels across the entire colorectum.4
In summary, the incidence of CRC in young adults in the USA is significantly higher than that in Europe, and the specific reasons for this difference need to be studied in depth, which may help to take specific measures to reduce the incidence of CRC.
PL and JZ are joint senior authors.
TW, PL, XZ and WZ contributed equally.
Contributors Drafting of the manuscript: TW. Study concept and design: PL. Acquisition, analysis or interpretation of data: all authors. Critical revision of the manuscript for important intellectual content: all authors. Statistical analysis: PL and XZ. Study supervision: JZ.
Funding This work was supported by the National Natural Science Foundation of China (grant numbers 81672267, 81772457 and 81871859) ，the Province Natural Science Foundation of Guangdong (grant numbers 2016A030313632 and 2017A030313567) and Guangzhou science and technology project (grant number 201804010200).
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; internally peer reviewed.