Women and clinicians are regularly reminded about the threat of breast cancer by the media, advertisements, and the experiences of friends or family members who are fighting the disease. And there is good reason for breast cancer to be prominent in our consciousness: The breast is the leading site of cancer in US women (32% of all cancers); however, probably because of smoking, cancers of the lung and bronchus have surpassed cancer of the breast as causes of cancer death in women. Every year in the US, there are about 212,000 new cases of invasive breast cancer and 56,000 new cases of in situ breast cancer.
The good news is that since 1990, incidence of breast cancer has plateaued, increasing only in women older than age 50 years at a rate of about 0.4% per year, and has been limited to localized disease. Mortality rates also began to decline in the 1990s. The 5-year survival rate for localized breast cancer (about 60% of cases) has risen from 72% in the 1940s to 97%.1 This trend, which is expected to continue, is attributable to earlier diagnosis as a result of greater utilization of screening mammography and increased use of chemotherapy. For clinicians who care for postmenopausal women, breast cancer is a major focus because it is increasingly frequent with age. About 94% of all breast cancers occur in women older than age 40 years, versus 15% in those younger than age 50 years, and only 6.5% in women younger than age 40 years.