The American Cancer Society has backed away from its long-standing recommendation that women over 40 get a mammogram once a year. The starting age now is 45 and, after age 54, the recommended frequency is every two years. The basis of this change is that mammograms produce many false-positives, which commonly lead to expensive and debilitating medical treatments that are not needed. [Although the ACS did not acknowledge it, there also is the fact that repeated mammogram radiation may actually cause cancer that is not present beforehand.] NY Times posted 2015 Oct 27
http://www.nytimes.com/2015/10/21/health/breast-cancer-screening-guidelines.html