PURPOSE: To compare immediate with delayed breast reconstruction in the setting of postmastectomy radiotherapy (PMRT) in terms of the total number of interventions and time required for breast cancer clearance and contour restoration. METHODS: The long-term prevalence and number of plannable and urgent interventions required in women receiving PMRT to finish 372 nipple-sparing or skin-sparing mastectomies combined with immediate implant-based breast reconstruction ([N]SSM/IIBR) were compared to those required for 18 mastectomies and delayed breast reconstruction (DBR) performed between 2013 and 2019. RESULTS: Re-interventions were required in 239 of the 372 breasts (64%) after [N]SSM/IIBR, whereas all 18 DBRs (100%) implicitly required at least one re-intervention (p <
0.002). Mastectomy and reconstruction necessitated a mean of 2.24 interventions per breast after [N]SSM/IIBR, which was significantly less than the mean of 3.72 interventions per breast after DBR (p <
0.002). Breast contour reconstruction was achieved in 14.3 months after [N]SSM/IIBR and in 38.6 months after DBR (p <
0.002). [N]SSM/IIBR required more class U3 urgent re-interventions than DBR (22% vs. 4%, p = 0.002), whereas DBR necessitated more class P3 plannable re-interventions (5% vs. 16%, p = 0.004). Initiation of PMRT is not postponed after [N]SSM/IIBR (10.1 weeks) compared to DBR (14.0 weeks). CONCLUSIONS: Women potentially needing PMRT should be informed pre-operatively that [N]SSM/IIBR with PMRT may be associated with 22% severe complications and 8% failure. Still, [N]SSM/IIBR prior to PMRT required less interventions and was less time-consuming than DBR following PMRT. Therefore, the potential need of re-interventions should not be the reason for refraining from [N]SSM/IIBR in these women.