By Roy, Mélissa;
Sebastiampillai, Stephanie; Zhong, Toni; Hofer, Stefan O. P.; O’Neill, Anne C.
Background: Microvascular breast reconstruction is a complex procedure that can be
associated with high complication rates. Although a number of individual
predictors of perioperative complications have been identified, few studies
have explored interaction between risk factors. Understanding the synergistic
effects of multiple risk factors is central to accurate and personalized
preoperative risk prediction.
Methods: The authors conducted a retrospective cohort study of patients who
underwent microvascular breast reconstruction at their institution between 2009
and 2017. All intraoperative and postoperative complications were recorded. A
multivariable logistic regression exploratory model identified independent
predictors of complications. Interactions between individual variables were
then assessed using the relative excess risk index (RERI) and the synergy index
(SI).
Results: Nine hundred twelve patients were included in the study and 26.1
percent experienced at least one perioperative complication. Obesity (OR, 1.54;
p = 0.009), immediate reconstruction (OR, 1.49; p = 0.028), and comorbidities
(OR, 1.43; p = 0.033) were identified as independent predictors of
complications. Obesity and comorbidities had significant synergistic
interactions with immediate reconstruction (RERI, 0.86; SI, 2.35; p = 0.0002;
and RERI, 0.54; SI, 1.78; p = 0.001), bilateral reconstruction (RERI, 0.12; SI,
1.15; p = 0.002; and RERI, 0.59; SI, 3.16; p = 0.005), and previous
radiotherapy (RERI, 0.62; SI, 4.43; p = 0.01; and RERI, 0.11; SI, 1.23; p =
0.040). Patients undergoing immediate breast reconstruction who were both obese
and smokers had a 12-fold increase in complication rates (OR, 12.68; 95 percent
CI, 1.36 to 118.46; p = 0.026) with a very strong synergistic interaction between
variables (RERI, 10.55; SI, 10.33).
Conclusion: Patient- and treatment-related variables interact in a synergistic
manner to increase the risk of complications following microvascular breast
reconstruction. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.
