According to a study by Karolinska Institutet, nearly three times as many people under the age of 50 in Sweden are diagnosed with colorectal cancer today compared with the early 1990s. The study also shows that mortality is elevated in both younger and older patients for up to ten years after diagnosis.
Published in Annals of Oncology, the study investigated trends in new cases of colorectal cancer in Sweden between 1993 and 2019. Covering more than 135,000 patients, it shows that the number of younger people under the age of 50 diagnosed with this cancer has increased over the past three decades.
For rectal cancer, new cases among younger people have increased by 2.04 percent per year; for left-sided and right-sided colon cancer, the increase is 2.41 percent and 2.64 percent per year, respectively. Over the entire period, this means that the disease has become two to three times more common in this age group.
The underlying causes of this increase are not fully understood. The researchers note that the trend does not appear to be driven by known risk factors for colorectal cancer in younger people, such as inflammatory bowel disease and hereditary factors. Instead, environmental and lifestyle factors early in life may play a role.
"Childhood obesity, a sedentary lifestyle, and antibiotic use have been suggested as contributing factors, although the underlying biological mechanisms remain unclear," says Cecilia Radkiewicz, researcher at the Department of Molecular Medicine and Surgery at Karolinska Institutet, who led the study.
Younger more often have advanced disease
The study also found that younger patients are more likely to have advanced (metastasized) disease at diagnosis compared with older patients, suggesting that symptoms may have gone unnoticed for longer before the cancer was detected.
"Since the chances of cure increase with early detection, it is important that both the public and healthcare professionals are aware that colorectal cancer can also affect younger people. At the same time, younger patients are more likely to tolerate extensive surgery and treatment, which is reflected in our results showing a more favourable prognosis compared with older patients," says Radkiewicz.
Another important finding is that mortality remains elevated in both younger and older patients for up to ten years after cancer diagnosis.
"This is remarkable, as patients are often considered cured after such a long time. Our results challenge this view and highlight the need for further research into the underlying causes, as well as long-term follow-up and support for both younger and older patients," says Radkiewicz.
The study was conducted in collaboration with Capio Sankt Görans Hospital and Södersjukhuset. The research was funded by Region Stockholm. The researchers report no conflicts of interest.
Publication
"Annals of Oncology Incidence Trends and Long-Term Survival in Early-Onset Colorectal Cancer: A Nationwide Swedish Study" , Shabane Barot, M.D Annelie Liljegren, Caroline Nordenvall, Johannes Blom, Cecilia Radkiewicz, Annals of Oncology, online August 14, 2025, doi: 10.1016/j.annonc.2025.07.019
