A global study looking at cancer diagnoses in the under 50s has found that early onset cancer has increased by 79.1 percent between 1990 and 2019.
The team, including experts from around the world, used data from the Global Burden of Disease dataset from 204 countries for their research. They found that during the studied time period, early-onset cancer deaths increased by 27.7 percent. Breast cancer was found to be the type of early-onset cancer with the highest morbidity, with a significant increase in regions of Asia, rising from 4.9 to 13.1 per 100,000 people in 1990 to 8.7–15.6 per 100k in 2019. Though the "growing prevalence of a westernized lifestyle" and better screening for cancer played a part in this, the team says that the factors driving this increase are still unclear.
"It is noteworthy that the incidence of early-onset breast cancer also increased in some countries without the introduction of routine screening, suggesting that the change of reproductive factors (younger age at menarche, oral contraceptive use, nulliparity, older age at first birth and never breast feeding), physical indicators (higher BMI) and behaviour factors (physical inactivity and alcohol consumption) during recent decades may have contributed to the increasing incidence of early-onset breast cancer," the team explained.
So, how worried should we be? Though increases in cancer may sound alarming, there are numerous factors at play.
"It’s important to note that this statement is based on absolute numbers rather than age-standardised rates, meaning these numbers do not account for changes in demographics such as increases in population size or aging of the population," Professor Montserrat García-Closas, Professor of Epidemiology at The Institute of Cancer Research, London, who was not involved in the study, told the Science Media Centre, adding that some increases (as the authors note) are down to improved screening and reporting.
"The increase in numbers of cancer deaths in this age group was notably lower than for diagnoses," Professor Dorothy Bennett, Professor of Cell Biology, St George’s, University of London, who was not involved in the study, added, "which is below the increases in total population and case numbers, indicating a fall in the average cancer death rate in this group."
Nevertheless, the team stressed that lifestyle factors were a driver behind cancer in people under 50, suggesting an area to focus on for improved prevention.
"Dietary risk factors, alcohol use and tobacco consumption were the main risk factors for top early-onset cancers in 2019," the team wrote in their conclusion. "Encouraging a healthy lifestyle, including a healthy diet, the restriction of tobacco and alcohol consumption and appropriate outdoor activity, could reduce the burden of early-onset cancer. It is worth exploring whether early screening and prevention programmes for early-onset cancer should be expanded to include individuals aged 40–44 and 45–49, but further systematic studies and randomized trials are necessary to make a definitive determination."
The study is published in BMJ Oncology.