Background: Uncertainty about prognosis and treatment of axillary lymph node-negative patients with estrogen receptor (ER)-negative or ER-positive invasive breast tumors of 1 cm or less prompted the analysis of data from five National Surgical Adjuvant Breast and Bowel Project randomized clinical trials. Methods: Two hundred thirty-five patients with ER-negative tumors and 1024 patients with ER-positive tumors were identified in these trials. Patients with ER-negative tumors received surgery alone or surgery and chemotherapy, Patients with ER-positive tumors received surgery alone; surgery and tamoxifen; or surgery, tamoxifen, and chemotherapy, End points were relapse-free survival (RFS), event-free survival, and overall survival. A result was considered to be statistically significant with a P value of .05 or less; all statistical tests were two-sided. Results: The 8-year RFS of women with ER-negative tumors who received surgery alone or with chemotherapy was 81% and 90%, respectively (P = .06), Survival was similar in both groups (93% and 91%; P = .65), The 8-year RFS of women with ER-positive tumors was 86% after surgery alone, 93% when tamoxifen was added (P = .01), and 95% after the addition of tamoxifen and chemotherapy (P = .07 compared with tamoxifen), Survival in the three groups was 90%, 92% (P = .41), and 97%, respectively. The difference between the latter two groups was significant (P = .01), Regardless of ER status or treatment, overall mortality was 8%; one half of the deaths were related to breast cancer. Several covariates affected the risk of recurrence in ER-negative and ER-positive patients. Risk was greater in women with tumors of 1 cm than in those with tumors of less than 1 cm, in women aged 49 years or younger than in those aged 50 years or older, and in women with infiltrating ductal or lobular carcinoma than in those with other histologic tumor types. Conclusions: Chemotherapy and/or tamoxifen should be considered for the treatment of women with ER-negative or ER-positive tumors of 1 cm or less and negative axillary lymph nodes.
