We defined the high-risk group as described above and found a high rate of recurrence in that subset. The remaining question is how many recurrences justify the recommendation for PMRT. Olivotto and Truong suggested that PMRT is indicated when LRR exceeds 25%, but not when it is < 10%, based on the magnitude of absolute LRR reduction and the absolute survival benefit (4:1 ratio according to the EBCTCG) . If the LRR rate is 12.8% (the 10-year rate in our high-risk group), patients’ priorities and preferences should be considered when making decisions regarding PMRT. The EBCTCG suggested a new ratio: for every 1.5 patients in whom AFR is avoided at 10 years, there is an additional survivor at 20 years . This works well for pT1-2N1 patients with mastectomy, but not for pT1-2N0 patients, as previously described . Despite the reduction in AFR by PMRT (34.2% in no-RT vs. 22.1% in RT at 10 years, 2p = 0.0003) in patients who underwent mastectomy and only axillary sampling, breast cancer mortality did not differ (35.8% in no-RT vs. 32.0% in RT at 20 years, 2p > 0.1). Even if PMRT reduced the AFR rate of 18.1% (the 10-year rate in our high-risk group) to a certain degree, it is reasonable that the absolute survival benefit would be small. This small survival benefit cannot be considered as grounds for routine use of PMRT for all high-risk patients with pT1-2N0 cancer. However, considering that most patients in our high-risk group were aged ≤ 40 years, even a small survival benefit may be important. Furthermore, the reduction in LRR or AFR would enable patients to work and live without a disease burden.