Luminal breast cancer is a highly endocrine responsive disease. However, the therapeutic benefit of chemotherapy (CT) in this population is not fully characterized. This study investigates the value of CT and hormone therapy (HT) in luminal breast cancer patients in the neoadjuvant setting.

Patients with operable breast cancer and immunophenotypically defined luminal disease (ER+/PR+/HER2-/cytokeratin 8/18+) were recruited. Patients were randomized to CT (epirubicin 90 mg/m(2) plus cyclophosphamide 600 mg/m(2) 4 cycles followed by docetaxel 100 mg/m(2 )4 cycles [EC-T]) or HT (exemestane 25 mg daily 24 weeks [combined with goserelin in premenopausal patients]). The primary end point was the clinical response measured by magnetic resonance imaging.

Ninety-five patients were randomized (47 CT, 48 HT). The clinical response rate was 66% for CT and 48% for HT (P = 0.075). We performed an unplanned analysis based on Ki67 levels (cut-off of 10%). Similar clinical response was seen between arms in patients with low Ki67 (CT: 63%, HT: 58%; P = 0.74); patients with high Ki67 had a better response with CT (67 versus 42%; P = 0.075). Grade 3/4 toxicity was more frequent with CT.

Luminal immunophenotype is not enough to identify patients who do not benefit from neoadjuvant CT. Luminal patients with low proliferation index could potentially avoid CT.