Influence of estrogen receptor status on response to combination chemotherapy for recurrent breast cancer

To determine the influence of cytoplasmic estrogen receptor (ER) status on response to chemotherapy among patients with recurrent breast cancer amenable to biopsy, we studied 65 patients who had ER determinations performed on metastatic lesions. The response to combination chemotherapy and duration of survival were determined in 49 of these patients who receive cytotoxic chemotherapy as their sole modality of treatment. Compared to patients with ER levels less than 3 femtomols/mg, patients with an ER concentration greater than or equal to femtomols/mg had a higher response rate (57% vs 21%, P less than 0.05) and a longer survival (35 vs 13 patients was attributable to response to subsequent hormonal manipulations. These differences between ER-positive and ER-negative patients were lessened by redefining ER-positive as greater than 10 femotomols/mg. Nevertheless, at our institution patients with ER-positive metastatic breast cancer have a higher response rate to chemotherapy and survive longer than their ER-negative counterparts.