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."
(JAMA. 2004; 292:1064-1073. Available post-embargo at JAMA.com)
Editor's Note: This work was supported by grants from the Helsinki University Central Hospital Research Funds, Sigrid Juselius Foundation, Yamanouchi European Foundation, and the Cancer Society of Finland.
Editorial: Do Tumors Detected by Mammography Screening Have a Favorable Prognosis?
In an accompanying editorial, Ruth M. O'Regan, M.D., of the Winship Cancer Institute, Emory University, Atlanta, writes that until further data area available, clinicians and researchers must use available prognostic and predictive factors to determine the best adjuvant (additional) 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 more than a useful, acceptable screening tool – it may actually select for patients with a favorable prognosis."
(JAMA. 2004; 292:1062-1063. Available post-embargo at JAMA.com)
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