Women who are obese get more aggressive ovarian cancers and are more likely to die from the disease, US scientists have found.
Obesity women may have more aggressive cancers
Experts already know obesity ups the risk of developing some cancers, but this study suggests fat tissue might also affect how a tumour progresses.
The authors believe fat cells excrete a hormone or protein that makes ovarian cancer cells grow more aggressively.
The Cedars-Sinai Medical Center research appears in the journal Cancer.
Lead researcher Dr Andrew Li said: "This study is the first to identify weight as an independent factor in ovarian cancer in disease progression and overall survival, suggesting that there is an element in the fat tissue itself that influences the outcome of this disease in obese women."
The researchers looked at the disease course of 216 women with epithelial ovarian cancer - the most common type of ovarian tumours, accounting for 90% of cases.
Comparison of the 35 women who were obese with the 108 women who were an ideal weight revealed significant differences in cancer outcomes.
Obesity influenced survival rates, shortened the length of time that the cancer recurred after treatment and led to earlier death from the cancer.
Dr Li said the next step would be to examine exactly how fat might influence tumour growth.
Other studies have found a compound called insulin-like growth factor 1 (IGF-1) is more highly expressed in obese people than those who are slimmer and IGF-1 correlates with increased breast cancer risk in women.
Also, a binding protein for IGF, called IGFBP-2, seems to promote invasion in ovarian cancer.
Around 6,800 women are diagnosed with cancer of the ovary every year in the UK. It can occur at any age, but is most common after the menopause.
Ovarian cancers are difficult to diagnose. Most women will be diagnosed with late disease and about 70% die within five years of being diagnosed, making it one of the most lethal cancers.
Dr Laura-Jane Armstrong, cancer information officer at Cancer Research UK, said: "Obesity increases the risk of cancer of the bowel, womb, gall bladder and oesophagus cancer, and of breast cancer in post-menopausal women so it is plausible that it could also increase a woman's risk of ovarian cancer.
"Indeed, several previous studies suggested this may be the case.
"However, this current study involved a relatively small number of patients so further research is needed to confirm if obesity can affect ovarian cancer progression.
"Maintaining a healthy weight is one of the best ways to reduce the chances of getting cancer."