Abstract Background The impact of progesterone receptor (PR) status on the prognosis of breast cancer after isolated locoregional recurrence (ILRR) remains unclear. This study assessed the prognostic impact of the PR status of ILRR tumors in patients with estrogen receptor-positive (ER+)/human epidermal growth factor receptor 2-negative (HER2-) breast cancer. Methods The study utilized data from the Japanese National Clinical Database (2004–2015), including 1,625 patients with ER+/HER2- ILRR. All participants were patients aged between 20 and 75 years at diagnosis who underwent curative surgery for ER+/HER2- primary breast cancer. Patients were classified into three groups based on the PR status of primary (p) and recurrent (r) tumors. We compared the overall survival (OS) and breast cancer-specific survival (BCSS) among the three groups using the Kaplan–Meier method with the log-rank test. ER and PR were considered positive if immunohistochemistry staining was positive in > 1% of tumor cells. For the ER expression levels in ILRR tumors, 1–10% were considered as ER-low positive. Results Patients with PR- ILRR (pPR-/rPR- and pPR+/rPR-) had significantly worse OS and BCSS than those with PR+ ILRR (pPR+/rPR+). Factors associated with worse outcomes included lymph node metastasis, a shorter disease-free interval, ER-low positivity, and no surgery for ILRR tumor. Conclusions This study highlights PR-negativity in ER+/HER2- ILRR tumors as a poor prognostic factor after ILRR, independent of the PR status of the primary breast cancer, emphasizing the need for tailored treatment strategies.
Murata et al. (Sun,) studied this question.
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