Annelotte van Bommel

80 MATERIAL AND METHODS Data source Data of the NABONBreast Cancer Audit (NBCA) was used to obtain information on breast cancer patients in the Netherlands. The NBCA is a national multidisciplinary quality improvement register inwhich all 92 hospitals in the Netherlands participate and is supported by the Dutch Institute for Clinical Auditing (DICA) and the Netherlands Comprehensive Cancer Organization (IKNL). 18 Information concerning patient, tumor, diagnostics and treatment is continuously collected prospectively either by the hospitals themselves or by data managers of the Netherlands Cancer Registry (NCR). Study population All female patients diagnosed with DCIS or invasive breast cancer between January 1 st , 2011 and December 31 st , 2013 who underwent amastectomy were selected. Hospital organizational factors based on data from the NBCA Hospitals were categorized as district hospital, teaching hospital (despite educational activities, not affiliated with a medical faculty), university hospital (hospitals having a medical faculty) or cancer specific hospital (hospitals only treating cancer patients). According to the number of new breast cancer patients annually diagnosed in a hospital, three groups were identified (group 1: 1–150, group 2: 150–300, group 3: >300 patients per year). The percentage of mastectomies (related to all surgical excisions) were categorized in three groups (group 1: 0–30%, group 2: 30–50% and group 3: >50%). Survey All 92 hospitals were invited to complete a web-based survey regarding hospital organization factors. Questions encompassed the number of weeklyMDTmeetings (1, 2, >2 times per week), the presence of the various disciplines involved in breast cancer care participating in the MDT meeting (e.g., nurse practitioners, pathologists, radiation oncologists, radiologists andmedical oncologists), number of plastic surgeons available at the institution per 100 new diagnoses of breast