Annelotte van Bommel

84 DCIS Hospital organizational factors such as hospital type, hospital volume, number of weekly MDT meetings, number of plastic surgeons per 100 new diagnoses and the attendance of a plastic surgeon at weekly MDTmeetings significantly affected IBR rates in univariable analyses. Consequently, these variables were included in the multivariable model ( Table 2 ). The percentage of mastectomies (related to all surgical excisions), and the number of breast surgeons available at the institution per 100 new diagnoses did not affect IBR rates significantly in univariable analyses and were therefore not included in multivariable analyses. Because age, SES and grade significantly affected IBR rates (data not shown) 10 , these factors were included in the multivariable model to correct for confounding ( Table 2 ). The multivariable model demonstrated that patients who underwent a mastectomy for DCIS at the cancer specific hospital had a higher chance of receiving IBR (OR=6.10 95%CI: 3.34–11.13) compared to patients receiving a mastectomy at a district hospital. Patients treated at a teaching (OR=1.33, 95%CI: 0.97–1.83) or university hospital (OR=0.97, 95%CI: 0.47–1.99) did not have a significant higher chance of receiving IBR compared to patients treated at a district hospital. The percentage of patients receiving IBR increased with an increasing number of plastic surgeons practicing in that specific hospital. Hospitals with more than 2.5 plastic surgeons per 100 diagnoses had a more than 3-fold higher IBR rate in comparison to hospitals with no or limited plastic surgeons available (OR=3.26, 95%CI: 1.11– 9.59). The structural attendance of a plastic surgeon at the weekly MDT meeting was significantly associated with a higher IBR rate compared to MDTs with no or incidental plastic surgeon attendance (OR=1.52, 95%CI: 1.10–2.10) ( Table 2 ).