Yearly mammograms for women between the ages of 40 and 50 dramatically reduce the chance that a mastectomy will be necessary if they develop breast cancer, a new study suggests.

British researchers studied the records of 156 women in that age range who had been diagnosed with breast cancer between 2003 and 2009, and treated at the London Breast Institute. Of these women, 114 had never had a mammogram and 42 had had at least one mammogram within the last two years, including 16 who had had a mammogram within one year.

About 19 percent of the women who'd been screened within one year had a mastectomy, the study found, compared with 46 percent of those who had not had a mammogram the previous year.

Because annual mammograms allowed tumors to be discovered earlier, breast-sparing surgery was possible for most of the women, said Dr. Nicholas M. Perry, the study's lead author.

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