Real-world Study of Pyrotinib-containing Regimens of Advanced HER2-positive Breast Cancer

• Pyrotinib (Drug): Pyrotinib: administered orally once daily at a dose of 400 mg, 320 mg or 240 mg within 30 minutes after breakfast. A continuous administration of 21 days is defined as one treatment cycle. The dosage of pyrotinib will be adjusted by physicians according to the individual clinical conditions. Concomitant chemotherapeutic agents and other supportive care treatments are determined at the investigators' discretion in accordance with clinical practice guidelines and drug instructions.
• Trastuzumab Rezetecan (Drug): Trastuzumab Rezetecan: administered intravenously at a dose of 4.8 mg/kg on Day 1 of each cycle, with a 21-day treatment cycle.

Primary outcomes

• rwPFS2 [From the start of first administration of pyrotinib-containing regimen (first-line or second-line) until disease progression or death occurring after the initiation of subsequent trastuzumab Rezetecan therapy，assessed up to 60 months.]: Second assessment of real-world progression-free survival (rwPFS2): defined as the time (in months) from the initial administration of pyrotinib-containing regimens (first-line pyrotinib combined with trastuzumab plus chemotherapy, or second-line pyrotinib combined with capecitabine) to disease progression or death after the initiation of subsequent Trastuzumab Rezetecan therapy.

Secondary outcomes

• rwPFS [From the start of initial pyrotinib treatment until the occurrence of disease progression, death, or switch to trastuzumab rezetecan due to intolerable toxicity，assessed up to 60 months.]: Real-world progression-free survival (rwPFS): defined as the time from the initial initiation of pyrotinib treatment to disease progression, death, or switch to Trastuzumab Rezetecan due to intolerable toxicity.
• OS [From the initiation of the study treatment regimen to death from any cause，assessed up to 60 months.]: Overall Survival (OS): defined as the time from the initiation of the study treatment regimen to death from any cause.
• rwORR [From the initiation of the study treatment regimen until disease progression or study withdrawal，assessed up to 60 months.]: Real-world Objective Response Rate (rwORR): refers to the percentage of subjects with a best overall response of CR or PR from the initiation of the study treatment regimen until disease progression and study withdrawal, among the total number of subjects in the analysis set.
• rwTTF [From the initiation of the study treatment regimen until disease progression or study withdrawal，assessed up to 60 months.]: Real-world Time to Treatment Failure (rwTTF): defined as the time from the date of treatment initiation to treatment discontinuation for any reason, including but not limited to disease progression, death, adverse drug reactions/toxicity, patient preference, and initiation of subsequent-line therapy.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

1. Aged ≥ 18 years old;
2. Histopathologically confirmed HER2-positive inoperable locally advanced or metastatic breast cancer;
3. Patients with first-line or second-line advanced disease:

   First-line advanced disease: no prior systemic therapy for locally advanced or metastatic disease. For patients who received neoadjuvant or adjuvant therapy, the disease-free interval (DFI) after the completion of the last chemotherapy or HER2-targeted therapy was more than 12 months; Second-line advanced disease: prior treatment with taxane combined with trastuzumab, with or without pertuzumab, in the advanced setting; or recurrence occurring during neoadjuvant/adjuvant therapy, or a disease-free interval (DFI) of ≤ 12 months after completion of the last neoadjuvant/adjuvant chemotherapy and HER2-targeted therapy;
4. Planned to receive pyrotinib-containing regimen, and judged by investigators based on clinical practice to have potential subsequent treatment with Ruikang trastuzumab after failure of pyrotinib-containing therapy;
5. Traceable medical records available throughout the treatment period.

Exclusion Criteria:

1. Failure to sign the informed consent form;
2. Pregnant or lactating females;
3. Patients participating in any interventional clinical trial involving investigational drugs or marketed drugs at enrollment;
4. Other conditions deemed ineligible for enrollment by the investigator's judgment.

• wang shu, Study chair, Peking University People's Hospital