Human Chorionic Gonadotropin in Breast Cancer Prevention

Breast cancer (BC) is the most common cancer diagnosed in American and Northern European women, and the number one cause of cancer-related death in nonsmokers (1, 2). Although a reduction in the mortality caused by this disease has been observed in the United States during the past few years, the incidence of BC is progressively and steadily increasing in most Western countries, and in societies that are becoming westernized (3–5). Although the reasons for this increase are uncertain, epidemiological and clinical evidence indicates that endocrinological and reproductive influences play major roles in this phenomenon. It has long been known that the incidence of BC is greater in nulliparous than in parous women (5–7). Changes in lifestyle, which in turn influence the endocrinology of women, have been observed during recent decades in American women, namely, a progressive decrease in the age of menarche (5) and a progressive increase in the age at which a woman bears her first child (6).