Annelotte van Bommel

68 Effect of case-mix adjustment on variation in IBR rates between hospitals Aftercase-mixcorrectionfortumorandpatientfactors(age,clinicaltumorstatus,clinical nodal status, multifocality, histology, grade, and receptor status), a slightly narrower but statistically significant variation in the use of IBR between hospitals was observed, ranging from0% to 43% ( Figure 1 ), compared to the initially observed variation. Ductal carcinoma in situ Variation in use of immediate breast reconstruction With an average rate of 42% (786/1881), IBR was more often performed after mastectomy for DCIS than for invasive breast cancer. Nineteen hospitals in 2011 and 17 hospitals in 2013 did not perform IBR for DCIS. IBR rates aftermastectomy for DCIS varied largely between hospitals (range 0–83%). The use of IBR slightly increased in 3 years;41%ofthepatientsreceivedIBRin2011(range0–100%)comparedto45%in2013 (range 0–83%) using unadjusted data. Most patients diagnosedwithDCIS received an implant-based reconstruction (86.1%). Autologous reconstruction and a combination of autologous and implant reconstruction were both performed in 5% of the patients undergoing IBR. The type of reconstructionwas unknown in 3.3%of the patients. Predictive factors for immediate breast reconstruction Factors potentially affecting the use of IBR followingmastectomy for DCISwere age, multifocality, andDCIS grade. Older patients (≥65 years) had anOR of 0.16 compared to patients agedbetween 50 and 65 years. Patientswithmultifocal disease had a 1.56- foldhigher chance of undergoing IBR thanpatientswithunifocal tumors (95%CI 1.22– 1.99). DCISgrade didnot have a statistically significant relationshipwith receiving IBR, and thereforewas not included inmultivariate analyses. Patient age andmultifocality remained statistically significant predictive factors in multivariate analyses. Table 4 shows univariate and multivariate analyses of factors predicting the use of IBR after mastectomy for DCIS. Effect of case-mix adjustment on variation in IBR rates between hospitals Case-mix adjustment of age and multifocality, enabling comparison between hospitals for IBR rates after mastectomy for DCIS, revealed a similar pattern as that of unadjusted data, with a variation between 0% and 74% ( Figure 2 ).