Biomarkers in Predicting Response to Tamoxifen and Letrozole in Postmenopausal Women With Primary Breast Cancer Treated on Clinical Trial CAN-NCIC-MA17

Quantitative Protein and Gene Expression Biomarkers of Tamoxifen and Letrozole Recurrence in the NCIC CTG MA.17 Cohort

RATIONALE: Studying samples of tumor tissue from patients with cancer in the laboratory may help doctors learn more about changes that occur in DNA and identify biomarkers related to cancer. It may also help doctors predict how well patients respond to treatment.

PURPOSE: This laboratory study is looking at biomarkers that may predict response to tamoxifen and letrozole in postmenopausal women with primary breast cancer treated on clinical trial CAN-NCIC-MA17.

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.

DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed primary invasive breast carcinoma resected at time of original diagnosis

• Treated on clinical trial CAN-NCIC-MA17

• Hormone receptor status:

  • Estrogen or progesterone receptor positive tumor

PATIENT CHARACTERISTICS:

• Female
• Postmenopausal

PRIOR CONCURRENT THERAPY:

• Not specified