Researchers from the Massachusetts General Hospital have reported that nearly three-quarters of breast cancer deaths occur among the minority off women who do not get regular screening mammograms. The details of this study were presented at the American Society of Clinical Oncology (ASCO) 2009 Breast Cancer Symposium held October 8-10 in San Francisco.

Breast cancer deaths are the second-leading cause of cancer death in U.S. women, although breast cancer mortality rates have been declining for the last 20 years.[1] The decline in mortality is thought to be due to improvements in both treatment and early detection.

Mammography is an important part of routine breast cancer screening. The American Cancer Society recommends that women at average risk of breast cancer receive annual mammograms starting at the age of 40.[2] Women at higher risk of breast cancer may need to begin screening at a younger age; as well, those at high risk may be screened with breast magnetic resonance imaging (MRI) in addition to mammography.

Studies have indicated that mammography reduces the risk of death from breast cancer. To explore the relationship between mammography and breast cancer mortality in the general population, researchers collected information about 6,997 women diagnosed with breast cancer in Massachusetts between 1990 and 1999 and followed until 2007 (median follow-up period was 12.5 years).[3]

Regular screening was defined as two or more screening mammograms at intervals of two years or less in women with no breast cancer symptoms. Surveys have indicated that roughly 80% of Massachusetts women over the age of 40 years have a screening mammogram at least every two years.

During follow-up, there were 461 deaths from breast cancer:

• 72 deaths (15.6%) were from non-palpable screen-detected cancers.
• 116 deaths (25.2%) were from palpable interval cancers in screened women.
• 322 deaths (69.9%) were in women who never had screening mammography.
• 23 deaths (5%) were in women who had not had a mammogram within two years of diagnosis.
• 345 deaths (75%) occurred in unscreened women or women who did not receive regular screening mammograms.
• 75% of breast cancer deaths occurred in the 20% of women who were not regularly screened, while 25% of deaths occurred in the 80% of women who were regularly screened.

When the researchers extrapolated these results to all women with breast cancer in the United States, they concluded that 5% of regularly screened women with breast cancer would die within 13 years compared with 56% of those who had not been regularly screened.

Comments: These results highlight the important role of regular screening mammography in reducing the risk of death from breast cancer.

References:

[1] American Cancer Society. Breast Cancer Facts & Figures 2009-2010. Available at: http://www.cancer.org/docroot/STT/STT_0.asp Accessed October 8, 2009.

[2] Smith RA, Cokkinides V, Brawley OW. Cancer screening in the United States, 2009: A review of current American Cancer Society guidelines and issues in cancer screening. CA: A Cancer Journal for Clinicians. 2009;59:27-41.

[3] Cady B, Webb M, Webb M, Michaelson J, Smith BI. Death from breast cancer occurs predominantly in women not participating in mammographic screening. Presented at the American Society of Clinical Oncology (ASCO) 2009 Breast Cancer Symposium. Abstract 24.