Survival outcomes in breast cancer patients with low estrogen/progesterone receptor expression.

INTRODUCTION: The prognostic value of low estrogen and progesterone receptors expression (ER/PgR 1%-10%) in early breast cancer patients is still unclear.

PATIENTS AND METHODS: We retrospectively analyzed 1424 consecutive patients with HER2/neu-negative and low endocrine receptors expression early breast cancer, submitted to surgery at the European Institute of Oncology between January 1995 and December 2009. Patients were classified according to the percentage of ER/PgR expression using immunohistochemistry. Group 1 with ER/PgR < 1%, and group 2 with ER/PgR 1% to 10%.

RESULTS: Group 1 (ER/PgR < 1%) included 1300 patients, and group 2 (ER/PgR 1%-10%) 124 patients. Median follow-up time was 74 months (range, 3-192 months). The 5-year disease-free survival (DFS) rate was 74% (95% confidence interval [CI], 72%-77%) for group 1, and 79% (95% CI, 70%-86%) for group 2 (P = .16). The 5-year overall survival (OS) rate was 86% (95% CI, 84%-88%) in group 1 and 90% (95% CI, 83%-95%) in group 2 (P = .13). In patients without lymph node involvement, the 5-year OS rate was 92% (95% CI, 89.5%-93.6%) for group 1 and 98% (95% CI, 90.2%-99.8%) for group 2 (P = .061). One hundred ten patients received endocrine therapy with no significant effect on DFS (P = .36) and OS (P = .30).

CONCLUSION: The ER/PgR 1%-10% group had a slight, but not statistically significant, better prognosis than the ER/PgR <1% group. Further studies are needed to identify the appropriate clinical approach in this subset of patients with low ER/PgR expression (ER/PgR 1%-10%), HER2-negative early breast cancer.