Lifelong excess weight almost doubles a woman’s risk of developing womb cancer, according to a Cancer Research UK-funded study published in BMC Medicine.
The international study looked at genetic samples from around 120,000 women from Australia, Belgium, Germany, Poland, Sweden, the UK, and the USA, of which around 13,000 had endometrial cancer, the most common type of womb cancer.
From these samples, researchers at the University of Bristol were able to identify hormones that may act as potential causal mechanisms linking excess weight to increased risk of endometrial cancer.
Uncovering the missing link
Being overweight or obese is the second highest preventable cause of cancer in the UK. It’s estimated that more than 1 in 20 cancer cases in the UK are caused by excess weight.
Womb cancer is one of the cancer types most closely linked with obesity.
It’s the most common gynaecological cancer in high income countries and is the fourth most common cancer for women in the UK – 1 in 36 women will be diagnosed in their lifetime.
And of UK womb cancer cases, it’s estimated that around a third are caused by being overweight or obese.
This large statistical analysis is one of the first studies of its kind to look at the effect of lifelong greater body mass index (BMI) on womb cancer risk.
On an individual level, BMI is not a single perfect metric for determining a person’s health, as it is calculated solely from their height and weight. However, in general, the higher a person’s BMI, the more fat they tend to carry.
This makes BMI easily scalable, and therefore it is still considered a suitable proxy for tracking health in entire populations.
The researchers looked at genetic markers of 14 molecular traits that could link obesity and womb cancer.
They uncovered that obesity increases the levels of two hormones, fasting insulin and testosterone, and these hormones increased the risk of being diagnosed with womb cancer.
The study is one of the first to find that for every 5 extra BMI units, a woman’s risk of endometrial cancer is almost doubled, with an increase of 88%. 5 BMI units is the difference between the overweight and obese categories.
This risk increase is higher than most previous studies have reported and reflects lifelong weight status rather than a snapshot in time like most other studies.
“This study is an interesting first step into how genetic analyses could be used to uncover exactly how obesity causes cancer, and what can be done to tackle it,” said Emma Hazelwood, lead author of the paper.
“Links between obesity and womb cancer are well-known, but this is one of the largest studies that has looked into exactly why that is on a molecular level. We look forward to further research exploring how we can now use this information to help reduce the risk of cancer in people struggling with obesity.”
What does this mean?
By pinpointing exactly how obesity increases the risk of cancer, future research could investigate how drugs may be used to reduce or increase the level of these hormones in people already at a higher risk of cancer.
For example, drugs like metformin used in diabetes treatment can reduce a person’s levels of insulin, and research suggests this drug also affects cancer risk, though further study is required.
Lifestyle and dietary interventions encouraging maintenance of a healthy weight therefore remain as the basis for the prevention of womb cancers.
Dr Julie Sharp, head of health information at Cancer Research UK said: “Cancer Research UK has been leading the way in uncovering links between obesity and cancer for years. Studies like this bolster the fact that being overweight or obese is the second biggest cause of cancer in the UK and can help us start to pinpoint why. This will play a pivotal role in uncovering how to prevent and treat cancer in the future.
“More research is needed to investigate exactly which treatments and drugs could be used to manage cancer risk among people struggling with obesity. We already know that being overweight or obese increases your risk of developing 13 different types of cancer. To reduce your cancer risk, it’s important to maintain a healthy weight by eating a balanced diet and staying active.”
When Kath first started experiencing bleeding in 2013, she put it down to the menopause. Despite urges from her daughter to get checked out, she carried on doing the job she loved – working as a bra fitter in Debenhams Trafford.
But just before Christmas in 2013 she had a heavy bleed, which prompted her to make an appointment with the doctor.
In January 2014, Kath went to her GP and was referred to Royal Bolton Hospital, where she had a biopsy. She was diagnosed with womb cancer.
“When you hear the word cancer your mind runs riot, and I was thinking: ‘Am I going to live to see my grandchildren grow up?’” Kath said.
“I felt sick as I didn’t know what was going on. It was as though I was in a dream. I was devastated when I found out and cried with my husband holding my hand.”
Thankfully, Kath’s cancer was caught at the earliest possible stage, which meant she could have life-saving surgery to remove her ovaries and cervix. The operation removed all the cancer, which meant she didn’t need radiotherapy or chemotherapy, and she is now cancer free.
But her journey did not end there.
“After finishing my treatment, I wanted to make some changes,” Kath said. “We don’t know what caused my cancer, but I have to admit that I was carrying a few extra pounds. So now I exercise and eat better to be healthier. I also wanted to be a role model for my family.”
Kath takes part in Race For Life every year, raising both money and awareness about cancer.
“Reading some of the words on people’s backs about why they were running brought it all back to me about how important this is,” Kath said.
“My daughter’s notes said: ‘Running for our Mum who beat womb cancer!’”
“It’s worrying to see that womb cancer rates are on the rise, and although weight isn’t the only risk factor, I want to encourage other women to live healthily so that fewer women go through what I went through.
“I hope that my story helps others make a change in their life.”