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 cancer because of the decreasing size and lymph node involvement in invasive breast cancer and earlier presentation of noninvasive and invasive breast cancer. DESIGN AND MAIN OUTCOME ASSESSMENT: Cases (N=1001) of breast cancer from a tertiary and a community hospital between 1989 and 1993 were analyzed for invasion, size, nodal status, and change over time.
RESULTS: Ductal carcinoma in situ constituted 14% and 18% of the cancers at the two hospitals. At the tertiary and community hospitals, 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 invasive breast cancer. Twenty-nine percent and 28%, respectively, were 1 cm or less in diameter. Axillary nodal metastases occurred in only 31% of the invasive cancers (tertiary hospital); only 10% had more than three nodal metastases. In the T1a and T1b cases, nodal metastases occurred in only 10% and 43% of the positive nodes were solitary; only 16% had more than three nodal metastases. The proportion of ductal carcinoma in situ, T1a and T1b, and node-negative cases increased significantly 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 diameter. Therapy simplification will be logical because of very small size, low risk of recurrence after breast conservation, and excellent prognosis, and might include increased breast conservation, avoidance of axillary nodal dissection, and omission of radiation therapy to conserve breasts. Adjuvant therapy will be based on the prognostic features of the primary cancer and findings from careful histologic examination of the sentinel lymph nodes.