Early life factors in relation to breast cancer risk in postmenopausal women.

We evaluated the role of early life factors in a large, population-based, case-control study of breast cancer risk in postmenopausal women. Case women in Massachusetts, New Hampshire, and Wisconsin were ascertained through state cancer registries; control women were randomly selected from drivers license lists (50-65 years of age) or Medicare beneficiary lists (65-79 years of age). Information concerning factors of interest was obtained through structured telephone interviews.

Hormone replacement therapy in relation to breast cancer.

Context: Studies of long-term hormone replacement therapy (HRT) suggest an associated increased risk of breast cancer, but whether this association differs according to histologic type of cancer has not been extensively studied.

Objective: To determine whether the association between HRT and risk of breast cancer varies by HRT formulation and differs across histologic cancer types.

Design, Setting, And Participants: Nested case-control study among 705 postmenopausal women enrolled in the Group Health Cooperative of Puget Sound (GHC) who were aged 50 to 74 years and had primary invasive breast cancer diagnosed between July 1, 1990, and December 31, 1995 (cases), and 692 randomly selected aged-matched female members of GHC (controls).