Results The linked data set represented 32.8% of all early stage breast cancer cases recorded in the HTR during the study period. Due to the nature of the health plan, 79% of the cases were younger than 65 years. Women with early stage breast cancer living on Oahu were 70% more likely to receive BCS than women living on the outer islands. In the univariate analysis, older age at diagnosis, lower tumor stage, smaller tumor size, and well-differentiated tumor grade were related to receiving BCS. Ethnicity, comorbidity count, menopausal and marital status were not associated with treatment type.