Breast cancer is the most common cancer among American women, except for skin cancers. The chance of developing invasive breast cancer at some time in a woman's life is about 1 in 8 (12%). In 2009, an estimated 192,370 new cases of invasive breast cancer will be diagnosed among women in the United States.

In addition to invasive breast cancer, there will be about 62,280 new cases of carcinoma in situ (CIS) in 2009. CIS is non-invasive and is the earliest form of breast cancer.

After increasing for more than 2 decades, female breast cancer incidence rates decreased by 2.2% per year from 1999 to 2005. This decrease may be due at least in part to less use of hormone replacement therapy (HRT) after the results of the Women's Health Initiative were published in 2002. This study linked HRT use to an increased risk of breast cancer and heart diseases.

Breast cancer is the second leading cause of cancer death in women, exceeded only by lung cancer. The chance that breast cancer will be responsible for a woman's death is about 1 in 35 (about 3%). In 2009, about 40,610 women will die from breast cancer in the United States. Death rates from breast cancer have been declining since about 1990, with larger decreases in women younger than 50. These decreases are believed to be the result of earlier detection through screening and increased awareness, as well as improved treatment.

At this time there are about 2.5 million breast cancer survivors in the United States. (This includes both women still being treated and those who have completed treatment.) Survival rates are discussed in the section "How is breast cancer staged?"

Last Medical Review: 09/04/2008
Last Revised: 05/13/2009