There are 3.8 million survivors with first breast cancer who are at high risk of developing a second primary breast cancer, affecting 10-15% of survivors. Many women with first breast cancer have high levels of fear of a recurrence or a second breast cancer, even when their risk of low. There are currently no good prediction models to identify women at increased risk of developing a second primary breast cancer. Drs. John, Kurian, and Maecker will measure C-reactive protein (CRP), adiponectin, and cytokines in stored plasma samples that were collected from women diagnosed with their first breast cancer between 1995 and 2009. They have identified 245 women diagnosed with a second primary breast cancer during follow-up. They will measure these inflammatory biomarkers in 110 women with second primary breast cancer, and for comparison, in 110 women with first primary breast cancer only. They will evaluate associations between these inflammatory biomarkers and the risk of developing second primary breast cancer. Blood-based biomarkers that are predictive of a higher risk of developing second primary breast cancer could inform clinical practice and surveillance care of women with first breast cancer, reduce fear, and improve prediction models for second primary breast cancer.