Annelotte van Bommel

124 Table 1. Patient, tumor, treatment, and hospital characteristics. (continued) IBR No IBR Item (n=229) % (n=281) % P-value* Treatment characteristics Mastectomy b Bilateral therapeutic mastectomy 14 6% 14 5% <0.001 Therapeutic and contralateral prophylactic mastectomy 41 18% 11 4% Unilateral therapeutic mastectomy 174 76% 256 91% Radiotherapy Yes 39 17% 95 34% <0.001 Hormone therapy Yes 106 46% 149 53% 0.130 Chemotherapy Yes 106 46% 143 51% 0.301 Neo-adjuvant chemotherapy Yes 26 11% 47 17% 0.085 Hospital characteristics IBR hospital volume e Low 22 10% 51 18% 0.001 Medium 70 31% 106 38% High 137 60% 124 44% Breast cancer surgery hospital volume f Low 74 32% 114 40% 0.125 Medium 88 38% 101 36% High 67 30% 66 24% Hospital type g General hospital 84 37% 135 48% 0.002 Top clinical hospital 111 48% 127 45% Academic hospital (including breast cancer-specialized hospital) 34 15% 19 7% IBR, mastectomy with immediate breast reconstruction; No IBR, mastectomy without IBR; BMI, body mass index. * Chi-square tested a Totals do not match up due to missing values b self-reported c Socio-economic status (SES) of the patients was based on four-digit postal code at time of surgery. SES-scores are provided by the Netherlands Institute for Social Research (Sociaal Cultureel Planbureau) and divided into three groups based on the delivered rank numbers: low (1st-3rd deciles), intermediate (4th-7th) and high (8th-10 th ) SES. d Body Mass Index (BMI) based on body length and weight, according to WHO-definition. e Percentage of annual IBR for mastectomy patients per hospital, categorized as low (0% IBR), middle (1-15%) or high volume (>15%). f Number of surgical treated breast cancer patients per year (average over 2012-2014), categorized as low (<150), middle (150-249), and high (>250) volume. g Hospitals were categorized as either general, teaching, or academic hospitals (including breast cancer- specialized hospital).