OBJECTIVES:
* Assess the prognostic utility of the MGH 2-gene and the GHI 21-gene expression signatures in postmenopausal women with primary breast cancer treated with tamoxifen followed by either placebo or letrozole on clinical trial CAN-NCIC-MA17.
* Assess the ability of the MGH 2-gene and the GHI 21-gene expression signatures to predict responsiveness to letrozole.
* Compare the prognostic utility of quantitative immunofluorescence vs standard immunohistochemistry of estrogen receptor, progesterone receptor, HER-2, tumor aromatase, cyclooxygenase-2, GATA-3, and NAT-1 in these patients.
* Assess the ability of quantitative immunofluorescence and standard immunohistochemistry of these proteins to predict responsiveness to letrozole in these patients.
* Use gene discovery from formalin-fixed, paraffin-embedded tumor specimens to identify novel gene expression profiles that may predict outcome and responsiveness to letrozole in these patients.
OUTLINE: This is a controlled study.
Formalin-fixed, paraffin-embedded breast tumor tissue samples are analyzed for MGH 2-gene and GHI 21-gene expression signatures using real-time quantitative polymerase chain reaction. Immunohistochemistry and immunofluorescence are used for analysis of estrogen receptor, progesterone receptor, HER-1 and -2, aromatase, GATA-3, NAT-1, and cyclooxygenase-2. Microarray hybridization is used to identify novel gene expression signatures.
PROJECTED ACCRUAL: A total of 957 specimens will be accrued for this study.
