Letrozole and Fulvestrant Combination in Second Line or More for Estrogen Receptor Positive Metastatic Breast Cancer; Efficacy and Predictive Factors of Response

Background: Preclinical data show that complete estrogen blockade by both down regulating estrogen receptor and inhibiting estrogen synthesis, has greater effect on tumor growth than either treatment alone. Combination of an aromatase inhibitor and fulvestrant may be an optimal second line therapy by preventing activation of growth factor pathways and possible cross talk with ER. One clinical study has shown no benefit of adding anastrozole to fulvestrant at first relapse. No clinical data on combination letrozole and fulvestrant in the second line or more metastatic beast cancer setting is available.