Breast cancer patients who are overweight have more aggressive disease and are likely to die sooner, US researchers reported on Friday.
A dangerous type of breast cancer, known as inflammatory breast cancer, was seen in 45 per cent of obese patients, compared with 30 per cent of overweight patients and 15 per cent of patients of healthy weight.
"The more obese a patient is, the more aggressive the disease," said Dr Massimo Cristofanilli of the University of Texas M.D. Anderson Cancer Centre, who led the study.
"We are learning that the fat tissue may increase inflammation that leads to more aggressive disease."
Writing in the journal Clinical Cancer Research, Cristofanilli and colleagues said they studied 606 women with breast cancer that had spread within the breast.
They classified them according to body mass index or BMI, a globally accepted measure of obesity. People with BMIs of below 25 are considered normal, while 25-29 marks overweight and 30 or above is clinically obese.
After five years, 56.8 percent of obese women and 56.3 per cent of overweight women were still alive. But 67.4 per cent of the normal weight women had survived.
More than 56 per cent of women of normal weight survived 10 years, compared to 42.7 per cent of obese women and 41.8 per cent of overweight women.
"Obesity goes far beyond just how a person looks or any physical strain from carrying around extra weight. Particular attention should be paid to our overweight patients," Cristofanilli said.
Many studies have shown that the obese have a greater risk of several types of cancer. Last month British researchers reported in the Lancet medical journal that obesity can double the risk of leukemia, multiple myeloma, thyroid cancer, colon and kidney cancers.
Fat cells produce a range of hormones that could fuel cancer, researchers say.