There has been a rapid increase in the knowledge of breast cancer determinants but also a continuing increase in incidence of breast cancer, says Dr Franco Berrino, head of preventive and predictive medicine at the Istituto Nazionale Tumori in Milan, Italy.
The disease is the most common cancer among women in the European Union. Each year some 60,000 women in the European Union die of it (significantly more than in the US) and 150,000 new cases are reported. Approximately one woman in 10 in Europe will develop breast cancer at some point in her life, according to the European Parliament's Directorate-General for Research.
But, according to Dr Berrino, we now know of effective prevention strategies.
"Breast cancer risk can be reduced by avoiding hormone replacement therapy, increasing physical activity, not being overweight, and eating a more healthy diet," Dr Berrino will tell the 4th European Breast Cancer Conference in Hamburg, Germany.
High levels of sex hormones and insulin-like growth factors are associated with cancer risk and the typical western diet increases their biological effect.
"The problem with the diet of most people in the West is that it tends to include processed foods high in sugars and fats, too much red meat and dairy products, and not enough unrefined grains and vegetable products. This diet reduces the body's sensitivity to insulin, and this in turn stimulates the production of sex hormones and other growth factors, which are directly linked to breast cancer risk."
Eating more of the latter and less of the former food groups would not only reduce obesity, but would reduce the risk of several cancers, as well as cardiovascular and other chronic diseases, he says.
"There is no doubt at all that dietary factors play an important part in preventing cancer. Any sustainable health policy should include an element of dietary prevention," says Dr Berrino.
The scientist is currently looking at the effect of diet and hormonal risk factors in women carrying a mutated BRCA1 and BRCA 2 gene, the most common mutation found in breast cancer. These women have a very high lifetime risk of developing breast cancer, and most of them develop the disease in their 30s or 40s.
However, it is not clear why some mutation carriers develop the disease and others do not, nor why some develop it early and some much later in life. "Our hypothesis is that the incidence of breast cancer among mutation carriers depends on environmental factors, of which diet will be a major one," he argues.
Dr Berrino and his team are trying to understand the role of these factors through two studies: one based on dietary questionnaires to patients who developed breast cancer before the age of 40, 20 per cent of whom carry a BRCA mutation; and a prospective study on the role of IGF-1 and other hormone levels among mutation carriers.