Optimal Timing for Expander to Implant Exchange After Postmastectomy Radiation Therapy

Background: The optimal timing of tissue expander to implant exchange after postmastectomy radiation therapy (PMRT) remains unclear and is a source of variability in 2-stage breast reconstruction. Radiation-induced tissue changes are known to impair wound healing and increase the risk of infection, yet evidence defining a safe interval for second-stage reconstruction is limited and inconsistent across prior studies. This study aimed to identify the optimal time to undergo exchange after PMRT therapy to minimize postoperative complications. Methods: A multicenter retrospective cohort study was conducted on patients who underwent 2-stage breast reconstruction with PMRT to the tissue expander between 2016 and 2025. The primary outcome was 90-day complication rate after permanent implant placement. Patients were excluded if they received neoadjuvant radiation therapy, PMRT to permanent implants, or did not complete the second stage of breast reconstruction. Results: Final sample included 298 patients with an average age of 46.2±10.2 years and BMI of 25.5±5.0 kg/m 2 . The mean interval between PMRT completion and implant exchange was 8.2±5.4 months. The ROC analysis identified >6.87 months as the optimal interval delay (AUC=0.558). Patients who underwent earlier exchange (<6.87 mo) experienced an increased overall complication rate after second stage reconstruction (14.8% vs. 6.7%, P =0.025), primarily greater rates of major infection (8.7% vs. 2.7%, P =0.025) and wound dehiscence (9.4% vs. 3.4%, P =0.033). When adjusting for covariates on multivariable logistic regression, earlier exchange (<6.87 mo) remained independently associated with an increased risk of complication ( OR =2.255, 95% CI: 1.015-5.008, P =0.046). Conclusion: This study found that delaying second stage reconstruction until at least 6.87 months after PMRT was associated with the lowest risk of 90-day complications. Incorporating this timeframe into surgical decision-making may help optimize patient outcomes and improve preoperative risk counseling.