A large number of clinical studies have shown that HR-positive BC patients have a better relative prognosis but are not as sensitive to NACT as HR-negative BC patients [12]. However, NACT is an imperative method for luminal BC patients with relatively late stages. At present, the predictive factors for the efficiency of NACT in HR-positive BC patients have not been thoroughly elucidated, and whether the response to NACT could be predicted by semiquantified ER and PR has been a matter of debate [13].
In our study, patients with larger tumour size (≥ 4 cm) or higher percent expression of Ki67 (≥ 14%) could predict a better outcome after 4-cycle NACT treatment, which was in line with prior studies [8, 10, 11]. Unlike previous research from other institutes, the results of our multivariable logistic regression showed that postmenopausal BC patients are more likely to obtain a better clinical therapy response in NACT compared with premenopausal BCs. To the best of our knowledge, this is the first study to describe the impact of menstrual status on NACT in HR-positive BC patients.
We next assessed the interaction between quantified HR expression and clinical response. Similarly, pretreatment ER and PR expression could be used as predictors of response to NACT only for postmenopausal BC patients. This result is similar to that obtained in Raphael’s study, in which he concluded that a lower pretreatment ER expression predicted a higher clinical response rate. However, the effect of menopausal status was not discussed in his study [13]. The possible mechanism is that the oestrogen level may affect the sensitivity of tumour cells to chemotherapy [14]. Furthermore, it is well known that ER+/PR- tumours have a higher level of growth signalling than ER+/PR + tumours [15, 16]. However, in our study, there was no significant difference when analysing the response to NACT among various ER and PR status subgroups (ER+/PR + and ER+/PR- subgroups).
In the current study, the changes in ER and PR expression among non-pCR patients who received NACT were also investigated. According to our findings, decreased ER and/or PR levels were found in approximately 50% of the patients after NACT treatment. However, when considering the therapeutic response of NACT, the predictive roles of decreased ER and PR could only be observed in the Her-2 negative subgroup. This finding may be attributed to differences in tumour cell subtypes, which may activate dissimilar signalling pathways in response to chemotherapy. Another reason for this finding may be that Her-2-positive subtypes have complex growth-promoting mechanisms, which may be affected by molecularly targeted therapy drugs rather than chemotherapy [17].
Our study has the largest number of patients to date among studies exploring the relationship between semiquantitative HR and NACT treatment, but the major limitation of this study is that our data were obtained from only one single breast cancer centre, and the research followed a retrospective design. As is well known, low HR expression is be an adverse factor for endocrine therapy [12], and in this research, we observed a reduction in HR expression due to chemotherapy. Could decreased HR expression be beneficial to whole breast cancer treatment? How does it affect progression-free survival (PFS) or overall survival (OS) in patients? Further studies, especially long-term follow-up studies, should take these questions into consideration.
The results of this study showed that quantified HR expression can serve as a predictor of NACT treatment response in postmenopausal BC patients. Changes in HR expression can also predict the outcomes of patients in the ER+/Her-2 negative subgroup. However, in the premenopausal and ER+/Her-2-positive subgroups, these factors were not observed to have predictive functions. In clinical work, continued chemotherapy should be considered for patients with the aforementioned features.