Association between androgen receptor expression, Ki-67 and the 21-gene recurrence score in non-metastatic, lymph node-negative, estrogen receptor-positive and HER2-negative breast cancer

BackgroundThe mechanisms underlying the favourable prognosis of androgen receptor (AR) expression in breast cancer are unknown.MethodsThe associations between the 21-gene recurrence score (RS), AR, grade, mitotic score, Ki-67 and estrogen receptor (ER) and progesterone receptor (PgR) expression were explored in sequential women with lymph node-negative, ER-positive and HER2-negative breast cancer. Statistical significance of this exploratory study was defined as p3). Median RS was 15 (range 1–53). AR expression showed a minimally significant positive correlation with ER (R=0.37), but no correlation with Ki-67 (R=−0.18). In univariable analysis, AR (p=0.01), ER (p