Mammography screening reduces risk of distant tumor recurrence

Women who have breast cancer detected by mammography screening have a reduced risk of distant tumor recurrence than women with breast cancer detected outside of screening, according to a study in the September 1 issue of JAMA.

The incidence of cancerous tumors detected by mammography screening is increasing due to its expanding use, according to background information in the article. Selection of therapies for women diagnosed as having breast cancer is based on risk estimations for cancer recurrence.

Heikki Joensuu, M.D., of Helsinki University Central Hospital, Helsinki, Finland, and colleagues compared the survival outcomes of women with cancerous tumors detected by mammography screening with women whose tumors were detected outside of screening. The study included 2,842 women identified from the Finnish Cancer Registry as having breast cancer in 1991 or 1992. The average follow-up time was 9.5 years. The clinical, histopathological and biological features of the tumors were compared.

The researchers found that women with cancerous tumors detected by mammography screening had better estimated 10-year distant (other location in the body) disease-free survival than women with tumors found outside of screening. In analysis that included factors related to the biological aspects of the cancers, women with tumors detected outside of screening had a 90 percent increased risk for distant recurrence than women with tumors detected by mammography screening.

"Cancerous tumor detection in mammography screening was a favorable prognostic variable independent of the number of axillary lymph nodes, the primary tumor size, age at cancer detection, and the histological grade," the authors write. "Further research on factors related to cancer invasiveness and metastasis formation needs to be performed. For women with cancerous tumors detected by mammography screening, the risk of distant metastases may be overestimated unless the method of detection is taken into account in risk estimations."

Breast cancer rates have been climbing steadily in the United States and other industrialized countries since the 1940's. In 2002 in the United States alone, breast cancer struck an estimated 205,000 women and killed nearly 40,000.