Estrogen receptor negative breast cancer may be defined as distinct biologic subtype disease, more aggressive with a typical molecular portrait. [30] This subtype seems to have a poor prognosis and poor treatment options because these patients are not candidate to hormonal therapy. Novel treatment strategies focusing upon this subtype are necessary in the future. [31] There are reports of clinical benefit in estrogen receptor negative patients treated with dose-dense chemotherapy (see background CALGB 9741 and MIG-1 study). In the CALGB 9741 study, patients randomized to receive dose-dense regimens experienced severe toxicities during paclitaxel treatment leading to dose reduction in 7% and 5%respectively.