Women whose breast cancer was detected by mammographic screening have a reduced risk of distant tumor recurrence than women with breast cancer detected outside of screening, according to an article in the September 1st issue of the Journal of the American Medical Association.

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

Heikki Joensuu, M.D., and his Finnish colleagues compared survival outcomes of women with breast cancer detected by mammographic screening with those of 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 tumors detected by mammography screening had better estimated 10-year distant disease-free survival than women with tumors found outside of screening. In an analysis that included factors related to the biological aspects of tumors, women with tumors detected outside of screening had a 90 percent increased risk for distant recurrence than women with tumors detected by mammographic 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 wrote. “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.”

In an accompanying editorial, Ruth M. O’Regan, MD, wrote that until further data are available, clinicians and researchers must use available prognostic and predictive factors to determine the best adjuvant treatment, if any, for patients with breast cancer.

“Joensuu et al identified a group of patients with small, node-negative breast tumors that are detected by mammography screening and who have a risk of distant recurrence or death due to breast cancer of less than 10 percent at 10 years. In the United States, patients younger than 70 years with tumors measuring between 1 and 2 cm would likely be offered systemic therapy. In addition, some data suggest that adjuvant therapy can improve outcome in patients with even smaller tumors. Therefore, these results, if confirmed, could help determine which patients would truly benefit from systemic therapy. Although newer screening techniques, such as breast magnetic resonance imaging, are being actively investigated, these data suggest that mammography screening may be more than a useful, acceptable screening tool ? it may actually select for patients with a favorable prognosis.”