Between 1990 and 2019 the global number of cancer cases in under 50s increased by 79%, and the number of cancer deaths in under 50s increased by 28%, according to an international team of Chinese, American and British researchers.
While cancer and mortality rate varied across regions, countries, and cancer types, nations with a high-middle and middle sociodemographic index and individuals aged 40–49 years were particularly affected, with the highest rates of early onset cancers in 2019 occurring in North America, Australasia, and Western Europe.
Low to middle income countries were also affected, with the highest death rates among the under 50s in Oceania, Eastern Europe, and Central Asia, and in low to middle income countries, early onset cancer had a much greater impact on women than on men, in terms of both deaths and subsequent poor health.
Lead author, Dr Jianhui Zhao, pointed out that early-onset breast, tracheal, bronchus and lung, stomach and colorectal cancers showed the highest mortality and burden in 2019 and that dietary risk factors (diet high in red meat, low in fruits, high in sodium and low in milk, etc), alcohol consumption and tobacco use were the main risk factors underlying early-onset.
“Cancer is generally more prevalent in adults over 50 years, but the incidence of early-onset cancer has increased worldwide and compared to later-onset cancer, the increase of early-onset cancer has significant personal and societal ramifications,” he said.
“Moreover, early-onset cancer and the adverse impacts of some corresponding cancer treatments may result in additional health issues during subsequent life cycle, which would considerably increase the disease burden associated with early-onset cancers.”
“The majority of previous studies focused on regional and national variations in the incidence and death of all age cancer, and only a few studies have looked at the issue from a global perspective or the risk factors for younger adults.”
The team drew on data from the Global Burden of Disease 2019 Study for 29 cancers in 204 countries and regions, to examine the age-standardised incidence rate (ASIR) and age-standardised death rate (ASDR); disability-adjusted life years (DALYs); and contributory risk factors for all those aged 14 to 49; to estimate the annual percentage change between 1990 and 2019.
They found that in 2019, new cancer diagnoses among the under 50s totalled 3.26 million, an increase of 79% on the 1990 figure. Overall, breast cancer accounted for the largest number of these cases and associated deaths at 13.7 and 3.5/100,000 of the global population, respectively.
After breast cancer, the highest death toll and subsequent poor health were recorded among patients impacted by cancer of the windpipe, lung, stomach, and bowel, with the steepest increases in deaths among people with kidney or ovarian cancer.
New cases of early onset windpipe and prostate cancers rose the fastest, with estimated annual percentage changes of 2.28% and 2.23%, respectively. At the other end of the spectrum, early onset liver cancer fell by an estimated 2.88% every year.
Notably, the prediction model indicated that people aged 40–44 and 45–49, ASIR and ASDR trends predicted for 2020–2030 showed that a significant proportion of the population affected by early-onset cancer morbidity and mortality in the next 10 years.
“Based on the observed trends for the past three decades, the researchers estimated that the global number of new early onset cancer cases and associated deaths would rise by a further 31% and 21%, respectively, in 2030, with those in their 40s the most at risk,” Dr Zhao said.
“While genetic factors are likely to have a role, diets high in red meat and salt, and low in fruit and milk; alcohol consumption; and tobacco use are the main risk factors underlying the most common cancers among the under 50s, with physical inactivity, excess weight, and high blood sugar contributory factors.”
In 2019, the regions with the highest ASDR were Oceania (39.1 per 100k), Eastern Europe (33.7 per 100k) and Central Asia (31.8 per 100k), whereas the lowest were in high-income Asia Pacific (16.3 per 100k).
Of note, East Asia’s incident and death numbers of early-onset cancer were 814,749 and 268,709, respectively, ranking first among all regions. The greatest age standardised DALYs rates were in Oceania (1952.6 per 100k), while the lowest were in high-income Asia Pacific (840.6 per 100k) in 2019.
“Significant regional variations in the early-onset cancer spectrum can be ascribed to the local environment, lifestyle, and level of available medical treatment,” Dr Zhao explained.
“For example, in high-income North America, Australasia and Western Europe with high degree of development, the ASIRs in 2019 were higher than 125 per 100k, while the lowest were in Western Sub-Saharan Africa and Central Sub-Saharan Africa.”
The United Arab Emirates (1127.6%) Qatar (1089.5%) and Saudi Arabia (896.0%) exhibited the sharpest increases in the number of incident cases from 1990 to 2019, while Lithuania decreased by 30.9%, followed by Georgia (−30.0%) and Latvia (−29.0%).
The most pronounced change in the number of death and DALYs cases was also observed in the United Arab Emirates (850.6% and 803.7%), while Latvia (−52.1% and −51.9%) experienced the greatest decline.
In 2019, the highest ASIR and ASDR of early-onset cancer were in the USA (282.1 per 100k) and Solomon Islands (82.9 per 100k), while the lowest ASIR and ASDR were in Niger (31.0 per 100k) and Kuwait (9.5 per 100k).
Concerningly, 20 countries still had age standardised DALYs of more than 2,000 per 100k.
An accompanying editorial by Dr Ashleigh Hamilton from Queen’s University in Belfast, noted that “the findings…challenge perceptions of the type of cancer diagnosed in younger age groups.”
“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,” Dr Hamilton said.
“Prevention and early detection measures are urgently required, along with identifying optimal treatment strategies for early-onset cancers, which should include a holistic approach addressing the unique supportive care needs of younger patients.
“There is a pressing need for partnership, collaboration and resource distribution at a global level in order to achieve these aims.”