A risk stratification by hormonal receptors (ER, PgR) and HER-2 status in small (≤1 cm) invasive breast cancer: who might be possible candidates for adjuvant treatment?

As the use of screening mammography expands, the proportion of invasive breast cancer a parts per thousand currency sign1 cm is increasing. The aims of this study were: (1) to identify risk factors for systemic metastases in patients with a parts per thousand currency sign1 cm invasive breast cancer and (2) to investigate the patient groups at the greatest risk for metastases with such small tumors. Data were collected retrospectively from the breast cancer registry of our institution for patients with invasive breast cancer from October 1994 to December 2004. Of 4,036 patients who received curative breast cancer surgery, we identified 427 patients who had T1a or T1b breast cancer excluding 39 patients who received neoadjuvant chemotherapy. Ipsilateral axillary lymph node involvement was found in 13% (57/427) of patients at the time of surgery. A multivariate analysis was conducted in 370 (T1aN0, T1bN0) patients without lymph node involvement. In a Cox-regression model, HER-2 positive and triple negative (TN) groups were identified as independent risk factors to predict distant relapse-free survival (DRFS) [Hazard ratio (HR) 8.8, P = 0.003 for HER-2 positive group; HR 5.1, P = 0.026 for TN group] in T1bN0 tumors. Statistical significance was not maintained when the analysis was limited to T1aN0 tumors. Even though T1aN0 and T1bN0 tumors have a relatively low risk of systemic failure, anti-HER-2-directed therapy for HER-2 group and new innovative adjuvant systemic treatment for TNBC patients with T1bN0 tumors should be considered. Prospective adjuvant trials are warranted in these subgroups of patients.