Aiello Bowles et al. BMC Cancer 2012, 12:136 http://www.biomedcentral.com/1471-2407/12/136 levels, emphasizing the need for new standard, quality measures [3]. The University of Vermont Breast Cancer Surgical Out- comes (VBCSO) database was developed in 2003 to estab- lish the feasibility of measuring potential breast cancer surgical quality indicators [4]. The VBCSO database included 910 women diagnosed with breast cancer between April 1, 2003- March 30, 2008 who underwent initial breast cancer surgery at a single institution. Trained nurses abstracted medical record data on initial mastect- omy rate, close and positive margin rates, number of sur- geries, number of lymph nodes obtained during sentinel node biopsy and/or axillary dissection, use of intraopera- tive pathology assessment for sentinel nodes, and days between diagnosis and initial surgery. Subsequently, these data have demonstrated variation in surgical outcomes among surgeons who practice at one institution [4]. We extended the VBCSO database to three Cancer Research Network (CRN) health plans to develop a large, non-voluntary, multi-institution database to study breast cancer surgical quality. The CRN is a consortium of 14 non-profit research centers based in integrated healthcare delivery organizations within the HMO Research Network [5]. The purpose of this paper is to describe the combined Breast Cancer Surgical Outcomes (BRCASO) research database, structure, data elements, and study methods in detail, including important lessons learned in collecting surgical outcomes data. We plan to use these data to evaluate variation in surgical quality measures (initial mastectomy rate, initial partial mastect- omy positive margin rate, and initial partial mastectomy re-excision rate) by patient-, surgeon-, facility-, and region-level factors. Methods Data from the VBCSO database were combined with data from three CRN health plans (Group Health Cooperative, Kaiser Permanente Colorado, and Marshfield Clinic) to form a single, large, multi-site database called BRCASO, which resides at the Van Andel Research Institute (VARI). All study procedures were approved by Institu- tional Review Boards at the University of Vermont, VARI, and Kaiser Permanente Colorado (through coop- erative review for the CRN health plans); we received a waiver of consent to collect patient and provider-level data. The waiver was granted based on the fact that this study was a retrospective review of standard treatment data and of minimal risk to the patients; all identifiable information was kept at local sites, and only a deidenti- fied data set was shared for analysis and reporting. Study population A total of 6095 women ≥18 years old were diagnosed with stage 0-IV breast cancer between January 1, 2003 Page 2 of 7 and December 31, 2008. To be eligible for inclusion in the database, women had to have their initial breast can- cer surgery performed by a surgeon employed by the University of Vermont or one of the CRN health plans (including CRN health plan-contracted facilities). We included all women with ductal carcinoma in situ (DCIS), invasive ductal (IDC) or lobular carcinoma (ILC); all other breast pathologies were excluded. We also excluded males, women with initial surgery at an external facility by a non-CRN health plan-employed surgeon, women with breast cancer diagnosed on pro- phylactic mastectomy, and women with breast cancer diagnosed but never treated surgically. BRCASO database The BRCASO database is stored on a SQL server 2008 database at VARI, the primary site for this research. Because of the multi-site nature of this study, we fol- lowed strict security procedures to ensure confidentiality of data transfer to VARI. Figure 1 shows electronic lim- ited data sets from each CRN institution were collated at a single site (Kaiser Permanente Colorado), before transfer to VARI through a Secure File Transfer Proto- col (SFTP) site using Secure Shell (SSH2) encryption. The University of Vermont transferred electronic data directly to VARI using the same SFTP site. Figure 2 shows chart data were abstracted at individual institu- tions and entered into a secure (HTTPS) online web application hosted by VARI. VARI stored and collated all electronic and chart abstracted data behind their fire- wall, where they were only accessible to programmers and system administrators at VARI. Electronic administrative data Each CRN health plan collects electronic administrative data on inpatient and outpatient procedures, health plan enrollment, pharmacy dispensings, laboratory tests, and other elements as part of clinical care. Each health plan also links to their local Surveillance, Epidemiology and End Results (SEER) or state cancer registry. All electro- nic data elements for CRN sites are part of the Virtual Data Warehouse (VDW) where they are formatted in a standard fashion across sites, but the data themselves are housed at each individual site [5]. For BRCASO, a programmer at one site wrote programs to identify eligi- ble breast cancer cases and extract relevant administra- tive data that could be run against the VDW at each site. We extracted electronic information from: tumor registry data on diagnosis date, diagnosis type, laterality, estrogen and progesterone receptor status, and tumor grade; inpatient and outpatient Current Procedure Ter- minology (CPT-4) codes including date and type of pro- cedures (partial mastectomies, total mastectomies, and lymph node surgeries) with de-identified surgeon and