Abstract
BACKGROUND: Type 2 diabetes (T2D) is associated with increased risk of complications after breast cancer surgery. This study investigated systemic and surgical-site postoperative complications and the risk of early and late breast cancer recurrence and mortality, overall, and according to T2D status. METHODS: From the Danish Breast Cancer Group (DBCG) and Danish registries, a cohort of women with incident early-stage breast cancer diagnosed 1996-2017 was assembled. All women underwent mastectomy or breast-conserving surgery. Using diagnostic codes, systemic and surgical-site complications within 30 days of surgery were defined. Early recurrence (<10 years from diagnosis) was ascertained from the DBCG and late recurrence (≥10 years after diagnosis) via a validated registry-based algorithm. Incidence rates (IRs) per 1000 person-years were calculated, and Cox regression was used to estimate adjusted hazard ratios (aHRs) of early and late recurrence, and death, according to postoperative complications. Potential effect measure modification by T2D was evaluated. RESULTS: Among 58 198 women undergoing breast cancer surgery, 6285 (10.8%) had postoperative complications. Overall, 747 and 5756 women with and without complications developed early recurrence (IR: 19.7 and 17.9, aHR = 1.04, 95% c.i. 0.96, 1.13), whereas 314 and 3314 women developed late recurrence (IR: 23.9 and 26.0, and aHR = 0.90, 95% c.i. 0.80, 1.02). Prevalent T2D did not impact these findings. Women with postoperative complications had higher mortality rates than those without complications (aHR = 1.11; 95% c.i. 1.06, 1.16); especially those with T2D versus no T2D (aHR = 1.50; 95% c.i. 1.30, 1.73). CONCLUSION: Postoperative complications after breast cancer primary surgery did not impact recurrence risk but had a negative impact on survival, especially in women with T2D.