Research on the Potential Mechanisms Underlying the Efficacy Differences in Specific Neoadjuvant Treatment Regimens for Different Subtypes of Breast Cancer

This single-center, open, prospective, clinical cohort study plan recruited 71 patients with three subtypes of breast cancer: triple-negative type, HR+HER2-, and HR-HER2+. Based on the basic conditions of the enrolled patients, such as tumor stage, pathological classification, expression levels of tumor biomarkers, age and economic status of the patients, treatment plans suitable for the patients were formulated by referring to the recommended treatment methods for each subtype of breast cancer clearly stated in the 2023 edition of the CSCO Breast Cancer Diagnosis and Treatment Guidelines. Patients with triple-negative breast cancer: Group A received neoadjuvant chemotherapy combined with anti-PD1 immunotherapy (T-EC regimen combined with anti-PD1 treatment), Group B received neoadjuvant chemotherapy (T-EC regimen), and Group C received neoadjuvant anti-PD1 immunotherapy (patients explicitly refused chemotherapy). Based on the evaluation results of imaging efficacy before and after neoadjuvant therapy, patients in groups A and B were divided into two subgroups: treatment response and treatment resistance. Among them, 6 cases were selected from each of the two subgroups in group A for single-cell sequencing analysis. In Group B, 3 cases were selected from each of the two subgroups for single-cell sequencing analysis; Group C was expected to have a smaller population and no distinction was made regarding the therapeutic effect. Three cases were selected for single-cell sequencing analysis. Patients with HER2+HR- breast cancer: Group A received neoadjuvant chemotherapy combined with trastuzumab plus pertuzumab targeted therapy (EC-THP regimen), and Group B received neoadjuvant trastuzumab plus pertuzumab targeted therapy (HP regimen) (patients explicitly refused chemotherapy). Based on the preoperative imaging efficacy evaluation results of the patients in each treatment group, the patients were divided into two subgroups: treatment response and treatment resistance. Among them, 3 cases were selected from each of the two subgroups in group A for single-cell sequencing analysis, and 3 cases were selected from each of the two subgroups in Group B for single-cell sequencing analysis. Patients with HER2-HR+ breast cancer: Group A received neoadjuvant aromatase inhibitor combined with CDK4/6 inhibitor treatment (AI+CDK4/6i regimen), and Group B received neoadjuvant aromatase inhibitor treatment (AI monotherapy regimen). Based on the preoperative imaging efficacy evaluation results of the patients in each treatment group, the patients were divided into two subgroups: treatment response and treatment resistance. Three cases were selected from each subgroup of Group A and Group B for single-cell sequencing analysis.

Inclusion criteria

• Voluntary enrollment, able to understand and sign the informed consent form; 2) Female, aged 25 to 70; 3) Meet the indications for neoadjuvant therapy (based on the indicated population clearly defined in the 2023 CSCO Breast Cancer Diagnosis and Treatment Guidelines); 4) No previous systemic treatment for breast cancer; 5) The neoadjuvant treatment regimen met the inclusion requirements: triple-negative breast cancer (T-EC+antiPD-1/T-EC/antiPD-1) HER2+ HR-breast cancer (EC-THP/HP), HER2-HR+ breast cancer (AI/AI+CDK4/6i); 6) Tumor specimens can be obtained (including puncture, minimally invasive, incision biopsy, and surgery); 7) A complete pathological report can be obtained. 4.2 Exclusion Criteria:

• The patient did not sign the informed consent form;
• Tumor specimens cannot be obtained (including puncture, minimally invasive, incision biopsy, and surgery);
• Patients with severe systemic infections or accompanied by other serious diseases;
• Have received cytotoxic chemotherapy, endocrine therapy, biological therapy or radiotherapy for any previous reason;
• Does not meet the indications for neoadjuvant therapy;
• Neoadjuvant treatment regimens are not included in the neoadjuvant treatment regimens defined in this study;
• Other circumstances where the researcher deems it unsuitable for inclusion. 4.3 Criteria for Subjects to withdraw from the study (1) All subjects can voluntarily withdraw at any stage of the study without being discriminated against or retaliated against, and their medical treatment will not be affected.

(2) Furthermore, the subjects may withdraw from this study under the following circumstances:

• Withdrawal decided by the researcher:

A: The patient does not meet the indications for the above-mentioned designated neoadjuvant regimen; B: In cases where the subjects are not suitable to continue the trial during the research process, such as when the patients cannot tolerate immunotherapy or chemotherapy, the established neoadjuvant treatment plan needs to be terminated; C: Those who accept the neoadjuvant treatment regimen specified in this study and show disease progression in the cycle evaluation need to terminate the neoadjuvant treatment in advance and undergo surgical resection of the tumor tissue.

D: Adverse events occurred. It was judged by the researchers that continuing to participate in the study would have an adverse impact on the safety of the subjects.

E: Subjects with poor compliance, which affects the assessment of tolerance; F: The researcher requests the subjects to withdraw from the study for any medical reason; G: The researchers believe that the subjects have other circumstances that make them unsuitable to continue participating in the trial.

• Voluntary withdrawal of the subjects:

A: The subject was unwilling to continue participating in the study and voluntarily withdrew the informed consent form.

B: Loss to follow-up (Before loss to follow-up, subjects who have completed three visits should be attempted to be contacted).

Inclusion criteria

• Voluntary enrollment, able to understand and sign the informed consent form;
• Female, aged 25 to 70;
• Meet the indications for neoadjuvant therapy (based on the indicated population clearly defined in the 2023 CSCO Breast Cancer Diagnosis and Treatment Guidelines);
• No previous systemic treatment for breast cancer;
• The neoadjuvant treatment regimen met the inclusion requirements: triple-negative breast cancer (T-EC+antiPD-1/T-EC/antiPD-1) HER2+ HR-breast cancer (EC-THP/HP), HER2-HR+ breast cancer (AI/AI+CDK4/6i);
• Tumor specimens can be obtained (including puncture, minimally invasive, incision biopsy, and surgery);
• A complete pathological report can be obtained.

Exclusion criteria

• The patient did not sign the informed consent form;
• Tumor specimens cannot be obtained (including puncture, minimally invasive, incision biopsy, and surgery);
• Patients with severe systemic infections or accompanied by other serious diseases;
• Have received cytotoxic chemotherapy, endocrine therapy, biological therapy or radiotherapy for any previous reason;
• Does not meet the indications for neoadjuvant therapy;
• Neoadjuvant treatment regimens are not included in the neoadjuvant treatment regimens defined in this study;
• Other circumstances where the researcher deems it unsuitable for inclusion. Criteria for Subjects to withdraw from the study (1) All subjects can voluntarily withdraw at any stage of the study without being discriminated against or retaliated against, and their medical treatment will not be affected.

(2) Furthermore, the subjects may withdraw from this study under the following circumstances:

• Withdrawal decided by the researcher:

A: The patient does not meet the indications for the above-mentioned designated neoadjuvant regimen; B: In cases where the subjects are not suitable to continue the trial during the research process, such as when the patients cannot tolerate immunotherapy or chemotherapy, the established neoadjuvant treatment plan needs to be terminated; C: Those who accept the neoadjuvant treatment regimen specified in this study and show disease progression in the cycle evaluation need to terminate the neoadjuvant treatment in advance and undergo surgical resection of the tumor tissue.

D: Adverse events occurred. It was judged by the researchers that continuing to participate in the study would have an adverse impact on the safety of the subjects.

E: Subjects with poor compliance, which affects the assessment of tolerance; F: The researcher requests the subjects to withdraw from the study for any medical reason; G: The researchers believe that the subjects have other circumstances that make them unsuitable to continue participating in the trial.

• Voluntary withdrawal of the subjects:

A: The subject was unwilling to continue participating in the study and voluntarily withdrew the informed consent form.

B: Loss to follow-up (Before loss to follow-up, subjects who have completed three visits should be attempted to be contacted).