Is womb cancer linked to waist size?

Obese women could be at greater risk of endometrial cancer, reports Sanjay Tanday

What is the story?
Women who are overweight are more likely to develop womb cancer than women who have a slimmer waistline, according to the media reports.

Canadian researchers found that women with a 34-inch waist, the average waist size for a British woman, were twice as likely to develop endometrial cancer as women with a 31-inch waist. Those with a BMI of 30kg/m2 or more and women who had put on over 44lb since the age of 20 were also found to be at almost double the normal risk of cancer.

Between 1992 and 2003, rates of endometrial cancer increased by 19 per cent, partly due to the rising levels of obesity.

The association of obesity in women and cancer is likely to be due to the excess fat carried around the stomach and chest area of obese women.

This results in higher levels of oestrogen, which can trigger endometrial cancer.

A quarter of women in the UK are now so overweight that their health is at serious risk, according to data complied by the EU statistical office.

Consequently, British women now top the EU league table for obesity, with 23 per cent clinically obese.

As many as one in five deaths from cancer are caused by being overweight, suggesting that in the region of 26,000 deaths a year could be avoided if adults keep to a healthy weight and diet, say the papers.

What is the research?
The reports are based on a cohort study that examined the association between obesity and the risk of endometrial cancer in 223,000 women aged between 35 and 70 who were recruited from 10 countries, including the UK.

Participants filled in a questionnaire on dietary, lifestyle and sociodemographic factors, as well as reproductive history and use of the Pill or HRT.

Measurements of weight, height, waist and hip circumference were taken at baseline and six-year follow-up.

Around 30 per cent of the cohort were overweight with a BMI of 25–30kg/m2 and 14.5 per cent were obese with a BMI greater than 30kg/m2.

Population-based cancer registries showed that 567 women developed endometrial cancer during the study period.

Body weight and BMI were found to be significantly associated with risk of endometrial cancer. Women with a BMI of 30–40kg/m2 were 78 per cent as likely to develop cancer as women with a BMI below 25kg/m2.

Women with a BMI greater than 40kg/m2 were three times more likely to develop cancer than women of a healthy weight.

However, overweight women did not have a statistically significant increased risk.

After adjustment for BMI, waist circumference was also a risk factor.

Women with a 34-inch waist were 50 per cent more likely to develop endometrial cancer than those with a waist circumference of 31 inches or less.

Hip circumference and waist-to-hip ratio were also associated with increased risk.

The association between excess weight and endometrial cancer risk was stronger among women who had never used oral contraceptives or HRT, compared with those who had used the medication.

The risk of endometrial cancer was also found to be particularly strong in postmenopausal women. Being obese or morbidly obese was associated with a 96 per cent increased risk of endometrial cancer among postmenopausal women, compared with 55 per cent among premenopausal participants.

The researchers proposed that in younger women the influence of obesity on hormonal levels occurred only at higher levels of being overweight, whereas among postmenopausal women, a more linear trend in cancer risk occurred.

In postmenopausal women, the proliferation of epithelial tissue in the endometrium is increased, as are somatic mutations and replication errors that can cause endometrial cancer.

What do the researchers say?
Lead researcher Professor Christine Friedenreich, from the department of population health and information at the Alberta Cancer Board in Canada, said this large study provides strong evidence that obesity and fat distribution could increase the risk of endometrial cancer.

‘Controlling weight gain and being overweight is one aspect of lifestyle that women have direct control over and that can greatly reduce their risks of developing several kinds of cancer,’ she said.

‘The message is positive and empowering as there is something that women can do to reduce their risk.’

However, the findings will need to be followed up with additional studies to confirm these results, said Professor Friedenreich.

What other researchers say?
Clinical director of the National Obesity Forum and Hertfordshire GP Dr David Haslam, welcomed the finding.

It is well known that obesity is linked to at least 20 different types of cancer, he said.

‘GPs should be advising worried patients that it is actually quite rare to develop endometrial cancer and is something that is unlikely to happen in epidemic proportions,’ he said.

‘But GPs should provide patients with advice about health and lifestyle to try to prevent obesity.’

Professor John Toy, medical director of Cancer Research UK, said the study findings add specific evidence to the theory that overweight women face a significantly increased risk of endometrial cancer.

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