Rising numbers of young men and women aged under 50 suffering from gastrointestinal cancers—as reflected in a new study in South Australia—is worrying international experts.

The long-term SA Cancer Registry data provides compelling evidence of a 'significant' increase in young-onset (18–50 years) gastrointestinal adenocarcinomas (cancers) over the past three decades, with Flinders University and other experts calling for greater efforts to understand and address the growing problem.

"The trend observed in the young cohort of oesophageal, stomach, colon and rectum, and pancreas cancer cases was not mirrored in older individuals aged over 50 years," says lead author Associate Professor Savio Barreto, from Flinders University, with SA Health and US colleagues in a new article in Cancers.

"This increased incidence, though apparent in both sexes, was more pronounced in men compared to women.

"Improved survival in the young-onset cohort was only seen in patients with colorectal cancers, but not those with cancer of the esophagus, stomach and pancreas.

The study calls for a concerted effort to determine the socio-demographic factors underlying this disturbing trend so that preventative strategies can be developed..

Between 1990 and 2017, the registry recorded a total 28,566 patients diagnosed with colorectal, pancreatic, stomach or esophageal adenocarcinomas. Of these, 2,129 (7.5%) were aged between 18–50 years.

The number of young adults with these cancers progressively increased from 650 in the 1990s (incidence rate of 9.3/100,000 people) to 759 in the last 8 years of the study (2010–2017, incidence rate of 12.89/100,000 people).

The incidence rate for these cancers has increased by 1% each year for males aged 18 to 50 years, says co-lead author Professor Claire Roberts.

"The biggest concern is that we don't know what the causes for this disturbing trend are," says Matthew Flinders Professor Claire Roberts.

"Young-onset carcinogenesis is an area that warrants urgent research. We need to identify potentially modifiable factors that could enable us to stem the rising incidence rates."

As well as the likely roles of nutrition, including poor quality diets and obesity, and drug and alcohol use, experts say exposures of these kinds before birth, and in early life, could accelerate cancer development resulting in a younger age at cancer diagnosis.

Other socio-demographic factors that need to be investigated include susceptibility of different ethnic groups and impacts of the levels of education and income, Associate Professor Barreto and University of California, Los Angeles Professor Stephen Pandol say in another new paper in Frontiers in Oncology.

The good news is that survival rates for gastrointestinal adenocarcinomas have progressively improved over the last 28 years for individuals over the age of 50 years, the researchers say. But this improvement has not been apparent in younger adults, in general, except for those with colorectal cancer.

The study authors intend to apply for funding to find answers to the questions this research has raised.

The article, Gastrointestinal Adenocarcinoma Incidence and Survival Trends in South Australia, 1990–2017 (January 2022) by Dominique Schell, Shahid Ullah, Mark E. Brooke-Smith, Paul Hollington, Marina Yeow, Christos S. Karapetis, David I. Watson, Stephen J. Pandol, Claire T. Roberts and Savio G. Barreto has been published in Cancers.