Abstract P3-03-10: The Impact of Type 2 Diabetes on Complications after Primary Breast Cancer Surgery: a Danish population-based cohort study
Authors: Kjærgaard Kasper , Wheler Jannik , Dihge Looket , Christiansen Peer , Borgquist Signe , Cronin-Fenton Deirdre 
Published: March 2023

Abstract
Introduction Type 2 diabetes (T2D) is associated with obesity and other comorbidities involving multiple organ systems, which may increase the risk of postsurgical complications. Knowledge is sparse on the impact of T2D on the postsurgical outcome after breast cancer (BC) surgery in primary BC. Objectives To investigate the association of T2D and risk of complications after primary BC surgery, and according to neoadjuvant chemotherapy. Methods Our cohort included all Danish women diagnosed with early-stage operable BC during 1996-2018 registered in the Danish Breast Cancer Group clinical database. All patients had primary surgical treatment—mastectomy or breast conserving surgery. Information on prevalent T2D was collected from Danish medical and prescription registries, defining T2D via diagnostic codes or redemption of ≥2 prescriptions for glucose-lowering drugs. We defined postoperative complications as hospital admissions for medical or surgical complications (re-operations (excluding seromas), bleeding, infection, thrombosis, kidney or arterial cardiovascular disease) up to 30 days after primary BC surgery. We calculated the 30-day cumulative incidence function (CIF) of postoperative complications and used Cox regression to estimate hazard ratios (HR) and associated 95% confidence intervals (95% CI) overall, and stratified by the receipt of neoadjuvant chemotherapy, adjusting for potential confounders. Results Among 84,491 women with operable BC, 4,669 (5.5%) had prevalent T2D at time of BC surgery. Overall, 800 (17.1%) and 8,621 (10.8%) of BC patients with and without T2D developed postoperative complications corresponding to CIFs of 17% (95%CI: 16% - 18%) and 11% (95%CI: 10% - 11%), respectively, and a HR of 1.44 (95%CI: 1.34-1.56). 173 (3.7%) BC patients with T2D and 2,805 (3.5%) without T2D received neoadjuvant chemotherapy. Among those who did not receive neoadjuvant chemotherapy, the CIFs of postoperative complications was 17% (95% CI: 16% - 18%) and 11% (95% CI: 10% - 11%) for women with and without T2D, respectively, with a corresponding HR of 1.42 (95% CI: 1.31-1.53). For those with and without T2D who received neoadjuvant chemotherapy, the CIFs were 24% (95% CI: 18% - 30%) and 10% (95% CI: 9% - 11%), respectively, and with a corresponding HR of 2.08 (95% CI: 1.49-2.91). Conclusion Among women with BC, prevalent T2D at the time of primary BC surgery increases the risk of postoperative complications. This excess risk is particularly pronounced among patients who undergo neoadjuvant chemotherapy.
Citation Format: Kasper Kjærgaard, Jannik Wheler, Looket Dihge, Peer Christiansen, Signe Borgquist, Deirdre Cronin-Fenton. The Impact of Type 2 Diabetes on Complications after Primary Breast Cancer Surgery: a Danish population-based cohort study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-03-10.