The indications for PMRT have traditionally been based on the risk of LRR. Although numerous studies have reported the prognostic value of clinicopathologic factors predicting LRR, such as patient age, menopausal status, tumor size, tumor grade, LVI, or resection margin status, variation exists in terms of the significance or magnitude of those factors in the setting of mastectomy without PMRT for pT1-2N0. Among them, young age and large tumor size, which were proven as significant prognostic factors in our analysis, are widely accepted variables associated with a high rate of LRR. With respect to patient age, Sharma et al. , Karlsson et al. , and Yildirim et al.  identified an age of ≤ 40 years as an independent predictor of high LRR, and Abi-Raad et al.  and Wallgren et al.  reported ages of ≤ 50 and ≤ 60 years as cutoffs, respectively. Similarly, Jagsi et al.  showed that a premenopausal status was an independent predictor of LRR. Regarding tumor size, T2 tumors (≥ 2 cm) were the most commonly reported cutoff point predicting a high risk of LRR [14–16].