What is causing the global rise in cancer among the young?

Breast cancer was the type with the highest number of cases in under-50s in 2019. The fastest increases since the Nineties, however, were in cancers of the windpipe and prostate.

The cancers accounting for the most deaths and disabilities in under-50s were breast, windpipe, lung, bowel and stomach.

Breast cancer had the highest number of cases in under-50s

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The data was analysed by an international team of researchers from institutions including Zhejiang University in China, the University of Edinburgh and Harvard University.

They said that while genetics probably play a role, the main risk factors behind the most common cancers in under-50s related to diet.

Physical inactivity, excess weight and high blood sugar are also “contributory factors” they said.

In a linked editorial, scientists from Queen’s University Belfast say the findings “challenge perceptions of the type of cancer diagnosed in younger age groups” and should prompt education of both public and healthcare professionals “regarding the possibility of certain cancers in younger adults to allow earlier diagnosis, which in turn improves outcomes”.

They said that while full understanding of the reasons behind the increasing trend remains elusive it was likely that lifestyle factors were contributing “and novel areas of research such as antibiotic usage, the gut microbiome, outdoor air pollution and early life exposures are being explored”.

The highest rates of early onset cancers in 2019 were in North America, Australasia and western Europe.

The researchers said that based on observed trends for the past three decades, they estimate the global number of new early onset cancer cases and associated deaths will rise by a further 31 per cent and 21 per cent, respectively, in 2030, with those in their forties the most at risk.

Statistics experts cautioned that looking simply at increasing cancer diagnosis numbers failed to take into account changes in population make-up over the same time period.

Dr Claire Knight, senior health information manager at Cancer Research UK, said: “It’s not fully clear what is driving the rise in early onset cancers, but exposure to risk factors in earlier life, better detection of cancer and genetics might all play a part.

“However alarming this might seem, cancer is primarily a disease of older age, with the majority of new cancer cases worldwide being diagnosed in those aged 50 and above.

“We need more research to examine the causes of early onset cancer for specific cancer types . . . If people are concerned about their cancer risk, there are lots of ways to help reduce this, such as not smoking, maintaining a balanced diet, getting plenty of exercise and staying safe in the sun.”

Professor Stephen Duffy, of the Centre for Prevention, Detection and Diagnosis at Queen Mary University of London, said the results were interesting. He highlighted decreases in levels of liver cancer, frequently caused by hepatitis B “for which there is effective vaccination” and rising cases of cancer in the windpipe, often caused by the Epstein-Barr virus “for which we do not have effective vaccination”.

He added: “The finding of an increasing trend of breast cancer incidence in women under 50 is consistent with what is happening to rates in the UK.

“Since we do not routinely screen women under 50, this is not due to increased diagnostic activity due to screening. It also suggests that similar increases over time in women aged over 50 who are offered screening, are not due to screening alone.

“Overall, there are many interesting results here, but they are complicated, and the cancer prevention and control community will need to take a long look at them over the next few weeks to consider exactly what they mean and what we can do to reverse some of the increasing trends.”

Screenings could do more harm than good

This is not the first study to report a rise in cancer cases in young adults, but it is the most comprehensive. Most have looked only at one country, or only one cancer (Kat Lay writes).

The research takes a global perspective and concludes cases are rising.

Some of this can be accounted for by rising population numbers, but this still means higher demand for health services.

The proposed solutions are not necessarily expensive. Many of the cancers at particularly high levels in young people are linked to unhealthy habits.

Making changes such as giving up smoking, limiting alcohol consumption, and following a healthy diet high in fruit and vegetables and low in red and processed meat, are all likely to reduce someone’s risk. Likewise boosting physical activity levels.

The researchers suggest exploring whether early screening programmes should be expanded to include people in their forties.

In the UK, breast screening begins at 50 and lung checks for current and former smokers at 55. Men over 50 can request prostate checks from their GP, although there is no national screening programme.

However, although cancers in the young are increasing, they remain relatively rare. This is likely to mean that the risk/benefit ratio for screening still tips the wrong way for most young people, with screening more likely to do harm than good.

Many experts suggest that rather than a blanket extension of screening to a particular age group, we need to get better at finding the people at highest risk — for example, because of the genes they carry — and keeping a close eye on them.