In addition, participants in certain trials were screened with mammography only, while for others a clinical exam was included. Also, the intervals between screenings varied, from 12 to 28 months depending on the trial. Concerns regarding the new recommendations for mammography screening are centered around the limitations of screening mammograms for women in their 40s. However, false positives are more common in younger women than older women. Of those women who have abnormal mammograms, for women ages 40-49 about 97 percent turn out not to have cancer compared to about 86 percent for women age 50 and older.
False negatives are more common in younger women than in older women.
The dense breast of younger women contain many glands and ligaments, which make breast cancers more difficult to spot in mammograms. Screening mammograms miss up to 25 percent of breast cancers in women in their forties compared with about 10 percent of cancers for older women. Younger women have a higher proportion of DCIS than older women. Approximately 45 percent of breast cancers detected by screening mammograms in women ages 40 to 49 are DCIS compared with about 20 to 30 percent of those detected in women age 50 or older. Convene an independent Mammography Data Monitoring Board to review on an ongoing basis the data from randomized mammography trials and to report regularly to the NCAB on the progress of the trials.