Randomized Phase II Trial of Letrozole plus Anti-MUC1 Antibody AS1402 in Hormone Receptor–Positive Locally Advanced or Metastatic Breast Cancer

Because adding AS1402 to letrozole did not improve outcomes compared with letrozole only, blocking ER may be a better strategy for harnessing MUC1 modulation of the ER to a clinical advantage. FcγRIIIa, FcγRIIa, and MUC1 allotype did not predict outcome for patients treated with letrozole with or without AS1402.