THE NEW ERA IN BREAST-CANCER - INVASION, SIZE, AND NODAL INVOLVEMENT DRAMATICALLY DECREASING AS A RESULT OF MAMMOGRAPHIC SCREENING

Objective: To describe the magnitude of changes and opportunities that may arise for simplified surgical procedures for women with breast ca ncer because of the decreasing size and lymph node involvement in inva sive breast cancer and earlier presentation of noninvasive and invasiv e breast cancer. Design and Main Outcome Assessment: Cases (N=1001) of breast cancer from a tertiary and a community hospital between 1989 a nd 1993 were analyzed for invasion, size, nodal status, and change ove r time. Results: Ductal carcinoma in situ constituted 14% and 18% of t he cancers at the two hospitals. At the tertiary and community hospita ls, the mean maximum diameters were 2.1 and 2.0 cm, respectively, and the median maximum diameters were 1.5 and 1.7 cm, respectively, for in vasive breast cancer. Twenty-nine percent and 28%, respectively, were 1 cm or less in diameter. Axillary nodal metastases occurred in only 3 1% of the invasive cancers (tertiary hospital); only 10% had more than three nodal metastases. In the T1a and T1b cases, nodal metastases oc curred in only 10%, and 43% of the positive nodes were solitary; only 16% had more than three nodal metastases. The proportion of ductal car cinoma in situ, T1a and T1b, and node-negative cases increased signifi cantly over time. Conclusions: Within the next decade, the proportion of all breast cancers that are ductal carcinoma in situ will approach 33%, and invasive cancers will approach 1 cm in median maximum diamete r. Therapy simplification will be logical because of very small size, low risk of recurrence after breast conservation, and excellent progno sis, and might include increased breast conservation, avoidance of axi llary nodal dissection, and omission of radiation therapy to conserved breasts: Adjuvant therapy will be based on the prognostic features of the primary cancer and findings from careful histologic examination o f the sentinel lymph nodes.