Tamoxifen Resistance in Breast Cancer

OBJECTIVES:

• Identify women who are resistant to tamoxifen citrate and other drugs for the treatment of breast cancer by testing their plasma for the presence of proteins (e.g., macrophage migration inhibition factor) encoded by resistance-inducing genes (RIGs).
• Provide retrospective data on the predictive value of RIGs to serve as the basis for a prospective clinical trial of these genes as predictors of drug resistance.

OUTLINE: This is a multicenter study. Patients are stratified according to response during tamoxifen citrate (TAM) therapy (resistant group [i.e., those who develop recurrent breast cancer while being treated with TAM] vs conditionally sensitive group [i.e., those who have disease-free survival for over 3 years after initial diagnosis while being treated with TAM]).

Patients undergo blood collection at baseline, within 3 weeks of initiation of TAM therapy, and then every 6 months for 3 years or until relapse, whichever comes first. Samples are analyzed by enzyme-linked immunosorbent assay for expression of protein biomarkers (i.e., kallikrein gene 10, macrophage migration inhibition factor, prolyl carboxypeptidase, queuine tRNA-ribosyltransferase, and kinesin) encoded by resistance-inducing genes. An additional blood sample is obtained from patients at the time of relapse, if available.

Patients also undergo assessment of medical history, personal habits, and characteristics of breast cancer (e.g., tumor histology, stage, and grade) at baseline.