How do you approach patients with low ER positive (1 - 9%) breast cancer?

The EBCTCG meta-analysis on adjuvant tamoxifen found benefit with tamoxifen use across all subgroups of ER expression, including the low expressors (1-9%). The absolute benefit of tamoxifen may not be significantly high. In my practice, I do offer anti-estrogen therapy in such a setting, but have a low threshold to discontinue if patients have intolerable side effects.

In the metastatic setting, it all depends on burden of metastatic disease. I have not had great success with anti-estrogen therap...