Annelotte van Bommel

60 ABSTRACT Background: The present study aimed to describe the use of immediate breast reconstruction (IBR) after mastectomy for invasive breast cancer and ductal carcinoma in situ (DCIS) in hospitals in the Netherlands and determine whether patient and tumor factors account for the variation. Methods: Patients undergoing mastectomy for primary invasive breast cancer or DCIS diagnosed between January 1, 2011 and December 31, 2013 were selected from the NABON Breast Cancer Audit. All the 92 hospitals in the Netherlands were included. The use of IBR in all hospitals was compared using unadjusted and adjusted analyses. Patient and tumor factors were evaluated by univariate and multivariate analyses. Results: In total, 16,953 patients underwent mastectomy: 15,072 for invasive breast cancer and 1,881 for DCIS. Unadjusted analyses revealed considerable variation between hospitals in postmastectomy IBR rates for invasive breast cancer (mean 17%; range 0–64%) and DCIS (mean 42%; range 0–83%). For DCIS, younger age and multifocal disease were factors that significantly increased IBR rates. For patients diagnosedwith invasive breast cancer, IBRwas more often used in younger patients, multifocal tumors, smaller tumors, tumors with a lower grade, absence of lymph node involvement, ductal carcinomas, or hormone-receptor positive/ HER2-positive tumors. After case-mix adjustments for these factors, the variation in the use of IBR between hospitals remained large (0–43% for invasive breast cancer and 0–74% for DCIS). Conclusions: A large variation between hospitals was found in postmastectomy IBR rates in the Netherlands for both invasive breast cancer and DCIS even after adjustment for patient and tumor factors.