October 1, 2009 (Berlin, Germany) — During the past few decades, the percentage of overweight and obese adults and children has steadily increased, which in turn has elevated the risk for certain cancers. That increase in risk might be substantial, according to the results of a new modeling study presented here at the 15th Congress of the European CanCer Organization and the 34th European Society for Medical Oncology Multidisciplinary Congress.

"In 2008, at least 124,000 new cancers in Europe may have been related to excess body weight," said study author Andrew Renehan, PhD, FRCS, FDS, a senior lecturer in cancer studies and surgery at the University of Manchester, United Kingdom.

These are very conservative estimates, and it's quite likely that the numbers are in fact higher.

"I must emphasize that we are trying not to be sensationalist about this," he added. "These are very conservative estimates, and it's quite likely that the numbers are in fact higher."

This number has substantially increased in the past 5 years. In 2002, there were 70,288 new cases of cancer related to excess body weight (Renehan et al. Int J Cancer. Published online before print July 30, 2009).

The sex differences also show an increase over the past few years, Dr. Renehan noted. In 2002, it was estimated that new cancers attributed to excess body weight affected 2.5% of men and 4.1% of women. By 2008, these proportions had increased to 3.2% of men and 8.6% of women.

"The proportion of new cancers attributable to a [body mass index] above 25 kg/m2 was highest among women in the Czech Republic, Latvia, Slovenia, and Bulgaria," Dr. Renehan said.

The analysis quantifies the burden of incident cancers attributable to excess body mass index in Europe, explained Dr. Renehan. The percentage of obesity-related cancers varied widely between the different countries, but the data were "broadly consistent" across geographic locations.

Percentages of Obesity-Related Cancers

Country % in Men % in Women
Denmark 2.4 2.1
United Kingdom 3.4 4.0
Germany 3.3 4.8
Czech Republic 3.5 8.2

Projected Figures Show Continuing Rise in New Cancers

In projecting the figures forward to 2008, the researchers took into account confounders such as rates of smoking and the use of hormone replacement therapy in postmenopausal women. Endometrial cancer (n = 33,421), postmenopausal breast cancer (n = 27,770), and colorectal cancer (n = 23,730) accounted for 65% of all cancers attributable to excess body weight.

After the Women's Health Initiative showed an association between hormone replacement therapy and risk for breast cancer, in 2002, the use of such therapy declined sharply. Hormone replacement therapy helped mask and dilute the effect of obesity on the incidence of breast cancer, Dr. Renehan explained.

But with fewer postmenopausal women using hormone therapy, the effect of excess weight on breast cancer risk is much clearer, he said. With declines in both smoking and the use of hormone replacement therapy, obesity could become the leading cause of cancer among European women.

With breast cancer and weight, there is no cutoff point, explained Jack Cuzick, PhD, head of the Department for Epidemiology, Mathematics and Statistics at the Wolfson Institute of Preventive Medicine in London, United Kingdom.

"There is a 1% increase in relative risk for every kilogram of excess weight," said Dr. Cuzick, who served as moderator for the session. "It's a continuum."

"People in Europe are gaining weight," said Dr. Renehan, "and it is projected to keep rising."

Multiple strategies are needed to circumvent the growing numbers of Europeans who are overweight and obese. There must be policy changes at national and international levels, lifestyle interventions, and new approaches, including pharmacologic interventions, he said. There is an "urgent need" to better understand the biologic and molecular mechanisms underpinning the link between obesity and different cancers.

15th Congress of the European CanCer Organization (ECCO 15) and the 34th European Society for Medical Oncology (34th ESMO) Multidisciplinary Congress: Abstract 327. Presented September 24, 2009.


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