Annelotte van Bommel

92 by Jagsi et al. Moreover, radiation therapy does not influence the effects of the hospital organizational factors in multivariable analysis. The current population-based study shows that multiple hospital organizational factors affect the use of IBR after mastectomy for DCIS and breast cancer in the Netherlands. Hospital type (cancer specific center), the number of plastic surgeons and the structural attendance of a plastic surgeon at the MDT meeting increased IBR rates significantly for both DCIS and non-metastatic invasive breast cancer. For invasive breast cancer, also the percentage of mastectomies related to all surgical excisions (>50%), >2 weekly MDTs and number of plastic surgeons available at the institution (>0.5 per 100 newdiagnoses) significantly increased IBR rates. Therefore, the use of IBR in breast cancer patients could be improved by optimization of these hospital organizational factors. Although the aim of the present study was not to stimulate performing more IBR in clinical practice, we feel that the availability of IBR for eligible patients should be more or less comparable between hospitals and unrelated to hospital organizational factors. However, hospital variation could only be partially explained by hospital organizational factors in the present study. A large variationwas found in theuseof IBR for DCISor invasivebreast cancer between hospitals thatwere included in the current study. The large variation is comparablewith other studies; IBR was performed in 21% of the mastectomy patients in the United Kingdomand24% in theUnitedStates. 2,11 Our data demonstrated that some hospitals tendednot toperform IBR, however, the referral rates for IBR revealed that therewere collaborations between hospitals. Therefore, it is possible that hospitals referred their patients toother hospitals incase IBRwas preferred. Likeothers,wedemonstrated that collaborationbetweenhospitals does not significantly affect IBR rates in thehospital of referral. AnEnglishnational study also reported similar hospital variation inperforming IBR after statistically correcting for hospital collaborations. 2 Different hospital organizational factors were investigated and appeared to be related to the use of IBR in the present study. For example, hospital type (cancer specific hospital) significantly affected IBR rates. Other nationwide studies also demonstrated the relationship between hospital type and IBR rates. 11,17 Alderman