RISK INCREASES WITH AGE (SIDEBAR)

Breast cancer is the leading cause of cancer death for U.S. women between 35 and 54, according to the National Alliance of Breast Cancer Organizations.

Breast cancer risk increases as a woman ages, if she has a family history of breast cancer, has never had children or had her first child after age 30. However, more than 70% of cases occur in women who have no identifiable risk factors, according to the alliance.

A woman in her 40s has a one in 66 chance of being diagnosed with breast cancer and about a one in 190 chance of dying from breast cancer that develops in that decade, according to data from the National Cancer Institute.

Regular mammograms starting at age 40 would lower the odds of dying to about one in 220.

This year, more than 30,000 women in their 40s will be diagnosed with breast cancer, and

a 15% reduction in mortality would mean more than 1,600 lives saved, the NCI says.

Regular screening mammograms can reveal breast cancer at its earliest stage, up to two years before it can be felt, according to the alliance.