Excess weight may raise the risk of developing breast cancer among postmenopausal women who have cardiovascular disease, according to a new study by the World Health Organization. The findings were published recently in the peer-reviewed journal CANCER, which is associated with the American Cancer Society.
Higher body mass index is already known to be a risk factor for breast cancer in postmenopausal women. This new study offers more detail on how the risk varies depending on whether the woman also develops cardiovascular disease or type 2 diabetes.
The researchers found that every 5 kg/m² increase in body mass index was linked to a 31 percent higher risk of breast cancer in women who developed cardiovascular disease during the study period. In women without cardiovascular disease, the increase in risk was 13 percent for the same rise in body mass index.
The development of type 2 diabetes did not appear to affect breast cancer risk. Whether or not a woman had type 2 diabetes, the link between higher body mass index and breast cancer remained similar.
The study team was led by Heinz Freisling from the International Agency for Research on Cancer, which is part of the World Health Organization.
ALSO READ: HPV behind growing cancer cases in young Indians, experts call for vaccination drive
Researchers used data from two large sources — the European Prospective Investigation into Cancer and Nutrition and the UK Biobank. The study involved 168,547 postmenopausal women who did not have type 2 diabetes or cardiovascular disease when they first joined the research.
After a median follow-up of 10.7 years in the European study and 10.9 years in the UK Biobank, 6,793 of the women were diagnosed with breast cancer.
The results also showed that the combination of being overweight and having cardiovascular disease led to 153 more cases of breast cancer per 100,000 women per year than expected. Being overweight was defined in the study as having a body mass index of 25 kg/m² or more.
The researchers suggested that the findings could help improve breast cancer screening by identifying women who face higher risk due to both excess weight and cardiovascular disease. They also encouraged future research to consider including women with a history of heart disease in weight loss trials aimed at preventing breast cancer.
The link between being overweight or obese and increased cancer risk is already well established. Excess weight is known to raise the risk for at least 12 types of cancer, including cancers of the uterus, kidney, liver, and colon.
A recent study published in Nature Communications reported that overweight and obese women are more likely to be diagnosed with larger tumours and more advanced-stage breast cancer.
