Study of Radiation Exposure and Bilateral Breast Cancer

Inclusion Criteria: * Eligibility for Cases: All women who meet the following eligibility requirements will be recruited as cases for the WECARE:GWA Study if they are not already cases (or refusers) from the parent WECARE Study: * Diagnosed since 1/1/1990 with a histologically confirmed first primary breast cancer (only invasive stage 1 or 2) while residing in one of the study enrollment site (cancer registry); * Diagnosed since 1/1/1992 with CBC (invasive only any stage) while residing in the same enrollment site (cancer registry); * Two years or longer time interval between first and second primaries; Between the ages of 18 and 54 at the time of diagnosis of the first primary; * Alive at time of contact; and * No history of previous or intervening cancer diagnosis, except cervical cancer in situ (CIS) or non-melanoma skin cancer. * Without bilateral mastectomy or prophylactic mastectomy of the contralateral breast following diagnosis of their first primary. Eligibility for Controls: Women who meet all of the following requirements will be eligible as controls. One matched control will be recruited for each participating case: * Diagnosed since 1/1/1990 with their first primary breast cancer (only invasive stage 1 or 2) while residing in one of the study enrollment site (i.e., cancer registry); * Between the ages of 18 and 54 at the time of diagnosis of the first primary; * Residing in the same study enrollment site (cancer registry) as when they were diagnosed with their…