Cancer Cases Surge in Under 50s Over the Last 3 Decades

New cases of early-onset cancers in the under 50s have risen by 79% globally over the past three decades, suggests a new study published in BMJ Oncology.

Trends in cancer statistics

Cancer is one of the leading causes of death globally, accounting for nearly 10 million deaths in 2020.

Lung cancers are the leading cause of cancer mortality, responsible for approximately 18% of cancer deaths. Breast cancers are the most common form, accounting for approximately 12% of all cancers, followed by lung (11%) and colorectal (10%).

Cancer is generally considered a disease of aging, being more common in older people. However, rates of early-onset cancers (i.e., occurring in those under the age of 50) have been on the rise. Current theories suggest that factors such as diet changes, obesity, physical activity or exposure to environmental pollution could be to blame.

Some studies have revealed insights into regional and national trends in cancer incidence (new cases) and mortality across all ages, but few have looked into early-onset cancers worldwide. The current study, led by researchers from Zhejiang University School of Medicine, sought to address this, exploring changes in the burden of early-onset cancers in recent decades.

Addressing changes in early-onset cancers

The researchers analyzed data from the Global Burden of Disease 2019 Study, which drew information from 204 countries and regions and included data on 29 different cancer types. This allowed them to calculate annual percentage changes in cancer incidence and deaths between 1990–2019.

They found that new cancer cases among the under 50s increased by 79% in 2019 compared to 1990 and that most of these cases and deaths were attributed to breast cancer.

The early-onset cancer types with the steepest rise across the last three decades were windpipe and prostate cancers, which saw annual increases of 2.28% and 2.23% respectively. However, early-onset liver cancer cases provide some optimism, falling by an estimated 2.88% every year across the same period.

Mortality figures present a bleaker picture, with over 1 million deaths from cancer among the under 50s in 2019 – an increase of around 28% since 1990.

Geographically, North America, Australasia and western Europe saw the highest rates of early-onset cancers in 2019 – though Oceania, eastern Europe and Central Asia had the highest mortality rates. Additionally, women in low- to middle-income countries were also more affected by early-onset cancer deaths than men.

Looking to the future, the researchers estimate from these trends that early-onset cancer cases and deaths will rise by 31% and 21% respectively in 2030.

The researchers suggest that genetic factors are likely to have a role in these trends, but that other factors such as inadequate diets, alcohol consumption and tobacco use are the main risk factors underlying the most common cancers among the under 50s, along with physical inactivity, excess weight and high blood sugar.

“Full understanding of the reasons driving the observed trends remains elusive, although lifestyle factors are likely contributing, and novel areas of research such as antibiotic usage, the gut microbiome, outdoor air pollution and early life exposures are being explored,” said the authors of a linked editorial.

“It is important to note that research on the drivers of early-onset cancer is currently quite limited,” said the study’s senior author Dr. Xue Li, speaking to Technology Networks. “We strongly encourage more researchers and funding support to be dedicated to the field of early-onset cancer. This will help elucidate the factors behind this phenomenon and ultimately reduce the social, economic and familial burden posed by early-onset cancer.”

Nevertheless, various limitations in the study’s findings have been noted by the researchers: for example, variations in quality of cancer registry data in different countries could lead to under-reporting and under-diagnosis. Additionally, the potential impact of early-life exposure to environmental factors on these trends remains unclear.

Reference: Zhao J, Xu L, Sun J, et al. Global trends in incidence, death, burden and risk factors of early-onset cancer from 1990 to 2019. BMJ Oncology. 2023. doi: 10.1136/bmjonc-2023-000049

This article is a rework of a press release issued by the British Medical Journal. Material has been edited for length and content.