By Alexa Lardieri

Doctors across the world are sounding the alarm over a surging epidemic of young people being diagnosed with cancers more commonly associated with the elderly.

Between 1990 and 2019, cases of cancer in young people across the globe have increased by 79 percent and deaths have risen 28 percent.

Studies project diagnoses will continue to rise by 31 percent and deaths will rise by 21 percent in 2030.

Nearly every continent is experiencing an increase of various types of cancer in people under 50 years old, which is particularly problematic as the disease tends to be caught in later stages in this population because most doctors aren't trained to look for it in young people.

The disparities of rates and types of the disease are puzzling scientists and have prompted some to kick off multi-decade research projects that will involve hundreds of thousands of people from around the world.

Globally, Australia has seen the highest number of early-onset cancer diagnoses in the world, with a rate of 135 per 100,000 people.

Nearby New Zealand has the second highest rate, at 119 cases in people under 50 per 100,000 people.

But while breast cancer is the top disease in Australia, colon cancer ranks first in its neighbor.

In Asia, Japan and South Korea may be close in proximity and similar economically, but they have different rates of early-onset colon cancer, which is increasing at a faster rate in South Korea.

The United States falls in sixth place, with 87 cases per 100,000 people under 50 years old and the UK takes the 28th spot, with 70.5 cases per 100,000 people.

Cancers increasing the fastest include throat and prostate cancers. Early-onset cancers with the highest mortality include beast, tracheal (windpipe), lung, stomach and colon.

Experts have longed speculated the increasing obesity rates and earlier cancer screenings may be behind the rise, as well as high-fat diets, alcohol consumption and tobacco use.

However, because lifestyles, habits and diets vary so widely from country-to-country, they now believe these factors do not entirely account for the surge.

Daniel Huang, a hepatologist at the National University of Singapore, said: 'Many have hypothesized that things like obesity and alcohol consumption might explain some of our findings. But it looks like you need a deeper dive into the data.'

More recent researchers have begun to focus on a genetic component to early-onset cancer. Some have found younger people develop more aggressive tumors than older patients, which are better at suppressing a person's immune system.

Pathologist Shuji Ogino at Harvard Medical School and his colleagues have also discovered a weakened immune response in people with early-onset tumors.

Still, however, the differences are subtle, Ogino said, and a clear reason cannot be determined.

A new field of research is the impact on early-onset cancer by the body's microbiome, the collection of all microbes, such as bacteria, fungi, viruses, and their genes, that naturally live in the human body.

The microbiome can be 'disrupted' by dietary changes and an increase in antibiotic use. The upsetting of the microbiome can lead to inflammation, which has been linked to an increase in several diseases, including cancer.

However, more extensive research on the matter needs to be conducted.

Of particular concern is colon cancer among young people. Data has shown the rate of cases among people ages 20 to 34 have risen 40 percent between 2010 and 2020.

And it is predicted they will rise 90 percent by 2030.

Cancers of the colon and rectum are the third most common type in the US and the third leading cause of death in both men and women.

The ACS estimates about 153,000 colorectal cancer cases will be detected this year, including 19,500 among those under 50 years old.

Approximately 53,000 people are expected to die from the disease.

As experts look to fight the epidemic, it was recently announced that a blood test to screen for colon cancer performed well in a study.

The test, made by Guardant Health, is not FDA-approved but is anticipated to be this year.

It looks for DNA fragments of tumor cells and precancerous growths and is for sale in the US for $895.

In the recent study, it caught 83 percent of cancers, but doctors still recommend people receive a colonoscopy - the gold screening standard - at varying ages based on their own risk factors.

Around the world, breast cancer is the disease seen most commonly in dozens of countries, including the US, UK, Canada, India, South Africa, Australia and Mexico, which may be due to more accessible screenings.

It is followed by prostate cancer, according to the World Health Organization.

To tackle the epidemic, researchers are beginning to collaborate between multiple countries to explore the subject, but experts stress that decades of data is going to need to be analyzed before the true reason is revealed.

Epidemiologist Barbara Cohn at the Public Health Institute in Oakland, California, said cancers can arise years after exposure to a possible carcinogen, such as cigarettes or chemicals.

She said: 'If the latent period is decades, then where do you look? We believe that you need to look as early as possible in life to understand this.'

In order to do that, scientists are looking to collect 60 years of data on thousands of people who have developed early-onset cancer around the world

A preliminary review of biological samples from expectant mothers dating back to 1959, whose children the researchers have followed since, found a possible connection between early-onset colon cancer and exposure in the womb to a synthetic version of the hormone progesterone, which is sometimes used to prevent a pre-term birth.

Dr Edward Kim, chief physician at City of Hope, a top cancer hospital in California, called cancer in young people 'a growing epidemic that we are observing in the clinic.'

Oncologists there said the rates of cancer in young people under 50 are highest for breast, colon and lung cancers.

While screenings have increased in some areas and cancer deaths in the US have fallen - though experts say the decline is not fast enough - cases of some cancers still continue to rise.

Brandon Arbini, 41, was diagnosed with stage 4 colon cancer and had to have one foot of his colon removed.

He said: 'Cancer, especially colon cancer, is not a disease of the elderly anymore. It's happening to more and more young people.'

Other cancers on the rise include uterine cancer - with rates rising two percent since the mid-1990s in people younger than 50.

Juliette Landgrave, diagnosed with triple-negative breast cancer at 38 years old, said she has seen women as young as 20 years old with the same disease.

Early-onset breast cancer cases increased by four percent each year between 2016 and 2019 - though deaths from the disease have fallen.

Landgrave said: 'I've seen in my triple negative cancer groups women that are 20; just starting their lives, being diagnosed with this horrible disease. So, I'm lucky that I was able to feel the lump and I was able to advocate for myself.'