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Obesity linked to rise in kidney cancer

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by Cancer Research UK | News

21 September 2002

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Kidney cancer is the fastest growing form of the disease in women, according to new statistics revealed by Cancer Research UK.

Figures show the incidence of the disease in women has increased by 22 per cent over the last ten years, a rate that overtakes the rise in female breast, skin and lung cancers, which have increased by 18, 15 and four per cent respectively over the same period.

Cigarette smoking is a major risk factor for kidney cancer but the increase in the disease is unlikely to be solely explained by smoking behaviour since the rapid increase is not seen in lung cancer. Experts at the charity believe that another key risk factor, obesity, could explain the continuing rise in the disease.

Dr Nick James, a kidney cancer expert at the Queen Elizabeth Hospital in Birmingham, says: “Obesity means that you are more than 40 per cent over the maximum desirable weight for your height and is probably the major risk factor for kidney cancer after smoking. American studies have shown that obesity can result in a four-fold increased risk of developing kidney cancer.”

UK trends show that in both men and women the numbers diagnosed as clinically obese are gradually rising, with over 20 per cent of the female population in this country now classified as obese.

Dr James explains: “Being overweight causes changes in hormones in the body, particularly for women and it could be this hormone imbalance that increases the risk of kidney cancer.”

Fat cells produce excess amounts of the female hormone oestrogen, which can speed up the natural process of cell division. The faster cells duplicate, the higher the chance that something can go wrong and a cancer cell is formed.

Dr James says: “The exact mechanism by which obesity can cause kidney cancer is likely to be complex. As well as higher oestrogen levels, fat cells can elevate levels of other hormones and chemicals in the body that may increase the risk of the disease.”

He added: “We don’t yet know whether the degree of obesity or the age that weight gain occurs makes a difference to the risk.”

Scientists at Cancer Research UK’s Cancer Epidemiology Unit in Oxford are currently analysing data on diet and weight gain during adulthood in relation to kidney cancer. They are also looking at other lifestyle factors that may contribute to the disease such as smoking, physical activity and alcohol intake and hope to announce preliminary results early next year.

Theresa Ridge (62), from Salisbury in Wiltshire, who was diagnosed with kidney cancer in March 2001, says: “I was tired all the time and had a pain in my groin so I went to my GP. He found blood in my urine and referred me to a specialist who diagnosed kidney cancer. I had my right kidney removed and luckily there has been no sign of cancer since.

“I’m very thankful my doctor was quick to act and my case was caught early enough for treatment. I think people need to be made aware of the early signs of the kidney cancer as well as what can cause it. I’m certainly surprised to hear that the disease is connected with smoking and weight gain.”

Sir Paul Nurse, Chief Executive of Cancer Research UK, says: “There is growing evidence that lifestyle factors have a big part to play in the development of kidney cancer. Health messages about the dangers of smoking are making an impact and we are seeing a decline in the numbers of smokers. We now need to make sure people are also aware of the problems obesity can bring.

He adds: “Cancer Research UK is concerned with carrying out the research needed to understand how obesity can affect cancer risk and what steps can be taken to reduce those risks.”