Widespread mammography screening has dramatically changed the presentation of breast cancer. Although the prospects for survival improve for women with a small tumor at diagnosis, a small percentage of women with tumors of less than 10 mm at diagnosis still die. Grade of malignancy and conventional prognostic factors are of limited value in predicting survival. Tabár and colleagues examined mammographic features of very small breast cancers (less than 14 mm) to elucidate predictors of long-term survival.
Data from large Swedish community studies of a screening mammography program conducted between 1977 and 1986 were reviewed to identify women diagnosed with invasive breast cancers of up to 14 mm in diameter. The presenting mammograms were classified into four categories based on the presence and pattern of calcifications. The women were followed until 1998, and the primary outcome was death from breast cancer.
A total of 346 tumors were classified as invasive. Median patient age at diagnosis was 65 years. More than one half of patients were treated by mastectomy with axillary dissection, and about one third required quadrantectomy with axillary dissection. The remaining women underwent mastectomy without axillary dissection or some other form of treatment. Systemic chemotherapy was not used. During the follow-up period (median: 16 years), 163 (47.5 percent) women died. The long-term survival rate in women with very small tumors (up to 9 mm) who had no casting-type calcifications was 95 percent. Overall 20-year survival was 87 percent; however, the survival rate was only 55 percent in those with casting-type calcifications. The 14 percent of women who had casting-type calcifications, even in very small tumors, accounted for 73 percent of the deaths.
The authors conclude that the presence of casting-type calcifications on screening mammography can signal early breast cancer with a particularly high risk of poor survival. They assert that these lesions behave like much larger tumors and require aggressive treatment. Women with evidence of these tumors should be recommended for surgical removal of tissue containing calcifications with a 1-cm tumor-free margin.
editor's note: Advising and supporting women through the implications of a “positive mammogram” seem to be increasingly complicated. While the general rule that smaller lesions have a better prognosis remains true, the results of this study suggest that physicians need to be increasingly sophisticated in developing treatment plans and offering advice about prognosis for each patient. These results also suggest that some patients with microscopic lesions will be well advised to undergo more extensive surgery and more intensive follow-up than others. Breast cancer is certainly more than one disease. If adverse prognostic features are present, even tiny lesions may merit extensive surgery.—a.d.w.