Cancer is increasing in younger age groups, largely because of poor lifestyle choices, diet and obesity, a global oncology review concluded.
But researchers also say the greater incidence could be the result of better screening programmes
The report, published in Nature Reviews Clinical Oncology, a monthly peer-reviewed academic journal, showed a significant increase in many types of cancer in those aged 50 or younger, including cancer of the breast, colon, oesophagus, kidney, liver and pancreas.
Scientists from the Harvard T H Chan School of Public Health, Boston in the US, evaluated the incidence of early onset cancers across several decades.
The review found the incidence of cancers in those under 50 has been rising in many parts of the world since the 1990s.
Changes in diet, lifestyle, obesity rates, environment and the microbiome ― microbes that are both helpful and potentially harmful and might interact with our genes ― are said to contribute to the higher rates of cancer in younger people.
The study’s senior author, Dr Shuji Ojino, an epidemiologist at Harvard Medical School and Brigham Women's Hospital, said the younger generation is facing a higher risk for many chronic diseases.
Alarming data on cancer - in pictures
"Cancer is just the tip of the iceberg,” he said. Several oncology studies dating back to the 1990s were evaluated for the study.
A focus was placed on specific cancers, and how common they were in young people.
They also looked at risk factors during early life and young adulthood.
Better screening also behind the surge in cancer cases
Increased use of screening programmes contributed to the phenomenon to a certain extent, although a genuine increase in the incidence of early-onset forms of several cancer types has also emerged, the report said.
Cancer risk varies depending on age group.
According to the American Cancer Society, people under 25 have a higher chance of lymphoma (a cancer of the lymphatic system), while women under 30 are more at risk from melanoma (the most serious type of skin cancer).
Breast, cervical, and colorectal cancer diagnoses, meanwhile, are more common after 25.
“The rising incidence of early onset cancers is partially attributable to increasing uptake of screening and early detection, for example, breast, thyroid and prostate cancers,” said Dr Gokul Sathyarathnam, a consultant oncologist at NMC Royal Hospital, Khalifa City in Abu Dhabi.
“But increasing incidence in several other organs, for example, colorectal, hepatobiliary and pancreatic cancers cannot be explained by screening.
“The reasons for this trend are not completely clear but are probably related to changes in risk factor exposures in early life or young adulthood.
“The increased consumption of highly processed foods which are low in fibres and rich in saturated fat and simple sugars, a meat-based diet together with changes in lifestyle, the environment and medical problems such as obesity might all be the culprits.”
Breast cancer in particular is on the increase, especially in younger women, and remains the number one cause of cancer deaths in women globally.
Other cancers becoming more common include pancreatic, colorectal, prostate and thyroid.
These cancers in particular are hormonal driven.
“One theory is that we are detecting cancer earlier, due to better imaging technology,” said Dana Haddad, consultant breast radiologist and head of breast imaging at HealthBay Polyclinic in Dubai.
“This is particularly true for breast cancer, because we can pick up in situ breast cancer on mammograms earlier, especially with population-based screening programmes.
“However, the 'birth cohort effect' demonstrates that certain cancers are occurring earlier with each new generation.
“In the UAE, we have a unique population with overall fewer senior citizens over the age of 65.
“This may also skew our perception of cancer diagnosis at an earlier age.”
While doctors are generally trained to identify cancers most commonly seen in younger people, such as lymphomas and sarcomas (a rare cancer of the bones and soft tissues), this latest review suggests doctors should be increasingly aware of more solid tumours as they become more common.
Processed foods are a big culprit - in pictures
Early check-ups advised for most common cancers
In the UAE, about 45 per cent of all cancer diagnoses in 2017 ― the most recent figures available ― were in people aged between 20 and 49, up from 42.3 per cent two years earlier.
Dr Humaid Al Shamsi, director of oncology at Burjeel Medical City in Abu Dhabi, suggested screening earlier for the most common cancers would enable a faster diagnosis.
“We know the numbers are quite high in the UAE, about 45 per cent of people under 50, so it is an eye opener here,” he said.
“In the past, we have not seen this high number, so we are trying to understand if this is a true figure or a result of better screening and medical conditions.”
In the UAE, breast cancer and colon cancer are screened for from the age of 40, rather than 45 or 50 in most other countries.
That age could reduce still further, said Dr Al Shamsi, who is also president of the Emirates Oncology Society.
“Many of my patients come to me late, when their cancer has already spread,” he said.
“We are aware of younger people developing cancer, so ideally we would like to begin screening earlier, even from the age of 30.
“It is something that we support because we cannot wait until people have more advanced cancers.
“Breast cancer and colon cancer are the most common, so we can check for this in younger people, rather than others like prostate cancer that generally occur in older people.”