Breast Density Requires Annual Mammography in Women Aged 40-49 Years

Breast Density Requires Annual Mammography in Women Aged 40-49 Years

According to a recent article published in the Journal of the National Cancer Institute, women between the ages of 40-49 require annual screening mammography to increase the rate of detection of breast cancer.

Breast cancer is diagnosed in approximately 250,000 women annually in the United States. If breast cancer is detected early, prior to spread, cure rates are high with standard treatment approaches. However, once the cancer has spread to distant sites in the body, most patients are considered incurable. Therefore, healthcare providers have focused efforts on regular screening to detect breast cancer in its earliest stages when it is most treatable. The optimal interval for screening mammography continues to be evaluated, with studies underway to determine specific subgroups of patients that may benefit from more or less frequent screening. For example, it is well known that screening mammography misses more breast cancers in women between the ages of 40 and 49 years than in women 50 years of age or older. Increased breast density in younger patients has been implicated as a major cause of this problem. Researchers believe that younger women may benefit from more frequent screening than elderly who are not considered at high risk.

Researchers from the University of Washington recently conducted a clinical study in an attempt to elucidate the reasons for missed detection of breast cancers with screening mammography. This study included 576 women who were diagnosed with breast cancer between 1988 and 1993. The researchers focused on the cancers that were diagnosed in between mammography screenings (interval cancers), with intervals of either 12 or 24 months between screenings. A variety of factors were compared between the younger (40-49 years) and older (>50 years) groups, including menopausal status, body mass index, family history, hormone use, tumor markers, mitotic figure count and Ki-67 index (measures of the speed of cellular replication), quality of mammography study, and breast density. When mammography was performed every 12 months, diagnosis of interval cancers occurred in almost 30% of younger women, compared to 14% of older women. When mammography was performed every 24 months, diagnosis of interval cancers occurred in over 50% of younger women, and 25% of older women. Two out of every 3 cases of interval cancers in women who were screened every 12 months were a result of missed cancers on mammography because of breast density. In women who were screened every 24 months, cancers were missed on mammography due to rapid cancer growth in 30% of the cases, while increased breast density accounted for another 38% of interval cancers.

The researchers concluded that annual screening mammography in women 40-49 years increases the rate of cancer detection compared to every 2 years, mainly due to breast density and rapid cancer growth. Women who are at a high risk of developing breast cancer may need to be on a more frequent screening schedule. Patients should speak with their physician about their individual risks and benefits of specific screening schedules for the early detection of breast cancer.

Reference: Buist DSM, Porter PL, Lehman C, et al. Factors contributing to mammography failure in women aged 40-49 years. Journal of the National Cancer Institute. 2004;96:1432-1440.

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