RATIONALE: Studying samples of tumor tissue and blood 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 patients will respond to treatment.

PURPOSE: This research study is looking at tumor and blood samples from postmenopausal women with primary breast cancer enrolled on clinical trial CAN-NCIC-MA27.

OBJECTIVES:

Primary

• To identify genetic variation, as measured by single nucleotide polymorphisms, that is associated with musculoskeletal adverse events in specimens from postmenopausal women with hormone receptor-positive primary breast cancer receiving adjuvant aromatase inhibitors and enrolled on clinical trial CAN-NCIC-MA27.

OUTLINE: This is a multicenter study.

DNA from tumor tissue and blood specimens that have been previously collected from patients are analyzed for single nucleotide polymorphisms.

DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed invasive breast cancer

  • Complete resection of primary tumor
  • Stage I-III (T1-3, N0-3, M0) disease

• Enrolled in clinical trial CAN-NCIC-MA27.

• No locally recurrent or metastatic breast cancer

• Hormone receptor status:

  • Estrogen receptor- or progesterone receptor-positive disease

PATIENT CHARACTERISTICS:

• Postmenopausal status, defined as one of the following:

  • At least 60 years old
  • Age 45-59 years with spontaneous cessation of menses for > 12 months prior to chemotherapy or study randomization
  • Age 45-59 years with cessation of menses for < 12 months or secondary to hysterectomy AND a follicle-stimulating hormone (FSH) level in the postmenopausal range (or > 34.4 IU/L)
  • Age 45-59 years on hormone replacement therapy (HRT) and discontinued HRT at diagnosis of breast cancer AND FSH level in the postmenopausal range (or > 34.4 IU/L)
  • Bilateral oophorectomy

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics

Participants in the MA.27 clinical trial who received either anastrozole or exemestane for adjuvant therapy of resected early breast cancer