Epidemiology of breast cancer, a paradigm of the “common soil” hypothesis

Breast cancer is the leading cause of death in women aged 20–50 years, with some geographical difference. The yearly incidence of the disease is increasing while the related mortality is steadily decreasing. Breast cancer is associated not only with specific hormones or factors related with reproduction, but mostly to more general environmental factors, linked to socioeconomic conditions and lifestyles (smoking, stress, physical exercise and particularly dietary habits). The latter, indeed, are risk factors or conditions common to hormone-dependent tumors and other chronic degenerative disorders, such as ischemic cardio cerebro-vascular and neuro-degenerative disease. Breast cancer can indeed be considered as a paradigm of the so-called “common soil” concept, according to which the above mentioned conditions, although having different clinical manifestations, share some pathogenetic mechanisms and risk factors and intermediate predisposing phenotypes (see Type2 diabetes, metabolic syndrome or obesity). In an epidemiological perspective, evidence has been accumulated on the common response of breast cancer and cardiovascular disorders to healthy lifestyles and in particular to the beneficial effects of a close adhesion to the Mediterranean dietary model. The latter would mainly be effective thanks to its anti-inflammatory properties, thus controlling the subclinical condition of low-grade inflammation, a common risk factor of all the “common soil” disorders. Results from the prospective cohort of the Moli-sani Study (nearly 25,000 adults from the general population of the Southern Italy region of Molise) are highly suggestive in this context. In a public health perspective, the “common soil” hypothesis may thus promote the application of preventive strategies, particularly targeting lifestyles, for a broad spectrum of widely prevalent disorders, ranging from breast cancer to myocardial infarction or cognitive impairment conditions.