Olivia Munn's doctor reveals the quick online test that flagged her cancer - and urges people in their 20s to take it

READ MORE: Is THIS what's causing mystery rise in young people's cancers?

With rates of cancer soaring among young people, oncologists are pleading with Americans to stay on top of their risk using simple tests that can be done at home.

The test that saved the life of actress Olivia Munn, who was recently given a shocking breast cancer diagnosis at age 43, is called the risk assessment tool, according to her gynecologist, eminent OBGYN Dr Thais Aliabadi.

Speaking at Fortune's Summit on cancer in young people this week, Dr Aliabadi said it is used by oncologists nationwide, and is recommended for some that are too young to be considered for mammograms.

While an inherited gene mutation is often considered the most important driver of early-onset cancer, experts increasingly warn that a collection of other factors that can strongly determine risk.

This includes a woman’s age during her first menstrual period, age at the time of the birth of a first child, and family history of breast cancer.

FIND DETAILS OF HOW TO DO THE TEST BELOW 

Olivia Munn has revealed she was diagnosed with luminal B breast cancer last year - having undergone four surgeries in the last 10 months. She credited her OBGYN (here) for 'saving my life'

Dr Thais Aliabadi insist that risk takes more than that into account, such as the woman’s age during her first menstrual period

Rates of breast cancer in under 50 year-olds have ticked up over the past two decades.

A recent study by Canadian researchers found that over the past 30 years, breast cancer rates in 20-somethings have rocketed 45 percent.

All types of the disease have shot up by a third in people under 50 over the last 20 years.

However, screening tools rarely apply to women aged below 40, leaving a gap that allows more women to fall through the cracks.

Such is the concern that the US Preventative Services Task Force has recently lowered the minimum screening age to 40, down from 50.

The breast cancer risk assessment administered by Dr Aliabadi was able to flag Olivia Munn’s risk, despite mammograms and other scans missing the tumor.

The most popular risk assessment tool is the National Cancer Institute’s Breast Cancer Risk Assessment Tool (BCRAT), sometimes known as the Gale Model after Dr. Mitchell Gail, who developed it in 1989. The test is accessible via the NCIBC website. 

Dr Aliabadi said: ‘If you’re tall, if you had children after 30, if you have dense breasts, if you have family history, if you’re overweight, you add your risk factors, and you get a risk score.

'If it’s 20 percent or above, that means you fall into the high-risk category and you have to start your imaging at early as 30, not 40, and you have to add MRI to it.

‘That’s exactly what i did for myself an Olivia Munn.’

Roughly 12 percent of US women will be diagnosed with breast cancer in their lifetime, studies show.

And Dr Aliabadi says it is challenging to predict which women will be within that 12 percent.

She continued: ‘Olivia had a negative mammogram, negative ultrasound, but because her lifetime risk was 37 percent, I added an MRI [a more detailed scan that can spot tumors in dense breasts].

'All of her friends were telling her why is your doctor so paranoid? And with my paranoia, she had three cancer lesions on her right and one on her left breast.’

Women who begin menstruating at an earlier age are exposed to estrogen for a longer time, making them more susceptible to cancer.

This also goes forwomen who go through menopause at a later age, as they are also exposed to estrogen for a longer period of their lives.

And pregnancy changes breast cells for the better, making them more resistant to cancer. Having a baby at an older age reduces that protective effect.

The test takes into account age, age at first menstrual period, age at the time of the birth of a first child (or has not given birth), family history of breast cancer (mother, sister or daughter), number of past breast biopsies, number of breast biopsies showing atypical hyperplasia, and race/ethnicity.

Ms Munn had a negative mammogram, negative ultrasound, but because her lifetime risk was 37 percent, Dr Thais Aliabadi added an MRI

While mammograms are recommended for women 40 and over, the DIY risk assessment tool can be done independently at home at any age.

A high-risk score is considered to be above 20 percent.

Read More

The ten-question cancer risk calculator that helped actress Olivia Munn discover her breast tumors can be done online - and doctors encourage women over 35 to take it

And with rates of cancer in under 40s ticking up, it can be a lifesaver. An MRI is not typically recommended as a screening test by itself because it can miss some cancers that a mammogram would find.

But it has been known to find that which is missed. Very high-risk women such as Olivia Munn are recommended to undergo a mammogram or an MRI every six months.

As well as dense breast tissue, an MRI can detect small lesions, and detailed information about a tumor, its size, shape, and reach.

However, doctors are often reluctant to order MRIs due to the risk of detecting false positives — lesions that would never become cancerous.

MRIs can also be prohibitively expensive, especially if a person does not have health insurance.

Dr Aliabadi says genetic testing that tells whether a person has genes that could raise their risk would also be helpful.