A Comparison of HER2 Positive and HER2 Negative Disease among a Large Population-Based Cohort of Breast Cancer Patients

The aims of this study are to: 1) Estimate the age-specific incidence of HER2+ breast cancer in the Northern California Kaiser Permanente membership. 2) Among breast cancer patients diagnosed between 2000 and 2005, compare demographic (e.g., age, race) and tumor (e.g., ER, PR, size, grade, nodal status) characteristics for those with HER2 positive and HER2 negative disease. 3) Among a random selection of HER2+ patients, collect additional information on cormorbid conditions of importance for treatment with Herceptin and/or entry into adjuvant clinical trials. 4) Compare the characteristics of HER2+ patients in the KP membership to those of patients entered into the standard adjuvant chemotherapy/Herceptin trials and estimate the percent of KP patients with HER2+ disease that would have been eligible for either of these trials.

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