RATIONALE: Collecting blood samples and health information from patients with invasive breast cancer and from their brothers and sisters over time may help the study of cancer in the future.

PURPOSE: This study is collecting blood samples and health information over time from patients with invasive breast cancer and from their brothers and sisters.

OBJECTIVES:

• Collect blood samples and medical and background information from patients with invasive breast cancer and their affected or unaffected siblings.

OUTLINE: Patients and their siblings undergo blood collection. They also complete medical and background questionnaires.

Patients and their siblings are followed annually for 5 years.

PROJECTED ACCRUAL: A total of 1,000 patients and siblings will be accrued for this study.

DISEASE CHARACTERISTICS:

• Meets 1 of the following criteria:

  • Pathologically confirmed invasive breast cancer (patient)

    • No ductal carcinoma in situ

  • Affected OR unaffected sibling

    • Affected sibling must have had (or currently has) breast cancer only
    • Unaffected sibling must be female
    • No deceased siblings
    • Must be a full-blood related sibling

• Patients receiving treatment on clinical trial ECOG-E1Y97 or ECOG-E3Y92 are not eligible

PATIENT CHARACTERISTICS:

• Not specified

PRIOR CONCURRENT THERAPY:

• Not specified