Weight gain linked to breast cancers says study
A new study has shed more light on the link between bodyweight and breast cancer risk in postmenopausal women.
The US study, led by Dr Heather Spencer Feigleson of the American Cancer Society, measured weight gain and breast cancer rates among 44,161 postmenopausal women who were not taking hormone therapy.
They found that the greater the weight gained after age 18, the greater the risk of all breast cancer types and stages. The risk of oestrogen-receptor positive tumours was particularly pronounced.
Women who gained 60 pounds during their adult years were shown to be almost twice as likely to have tumours in the ducts of their breasts (ductal carcinoma) when compared to women who gained 20 pounds or less.
They were also more than 1.5 times more likely to have cancer in the lobes of the breast (lobular carcinoma), more likely to have oestrogen receptor-positive tumours, and three times more likely to have tumours that had spread.
The researchers said the study reinforces previous findings suggesting that body fat, which increases the levels of oestrogen in the body, might boost tumour growth and so increase breast cancer rates in postmenopausal women, who do not produce oestrogen.
While previous studies have suggested a link between weight and breast cancer, this is the first to attempt to measure the risks of cancer relative to weight gained in adulthood.
Additionally, there has been some debate as to whether the link between bodyweight and breast cancer was due to the effects of higher oestrogen levels or due to the increased body mass interfering with screening.
The women in this study were all screened regularly, implying that the increase in risk was due to hormonal factors.
"These data further illustrate the relationship between adult weight gain and breast cancer, and the importance of maintaining healthy body weight through-out adulthood," the study concluded.
The research is published in the July issue of the journal Cancer.