This is a retrospective, single-arm real-world study based on the National Anticancer Drug Clinical Application Monitoring Network database.The aim of this study is to evaluate the efficacy and safety of paclitaxel liposome combined with anti-HER-2 monoclonal antibody as first-line salvage treatment for HER-2 positive advanced breast cancer. It seeks to understand the application patterns, efficacy, and safety of paclitaxel liposome combined with anti-HER-2 monoclonal antibody in real-world settings, providing patients with safer treatment options.

The National Anticancer Therapy Data Surveillance System (NATDSS) is the largest oncology diagnosis and treatment database in China to date, covering patient data from over 1400 oncology hospitals and integrated hospitals. It has collected data from approximately 15 million cancer patients since 2013, including mortality information obtained from the CDC death registration database.

Paclitaxel liposome was introduced to the market in 2004 as a formulation of paclitaxel. It utilizes nanotechnology to encapsulate the poorly water-soluble paclitaxel within a lipid bilayer of liposomes, solving the issue of paclitaxel& low solubility in water. Paclitaxel liposome no longer employs polyoxyethylated castor oil as a solvent. While ensuring efficacy, it reduces the risk of associated adverse drug reactions (such as severe allergic reactions), thereby enhancing the tolerance of cancer patients.

Although paclitaxel liposome is widely used in HER-2 positive advanced breast cancer, there is currently no research on the efficacy and safety of combining paclitaxel liposome with anti-HER-2 monoclonal antibodies as first-line salvage treatment of HER-2 positive advanced breast cancer.

This study aims to conduct a real-world study on the efficacy and safety of combining paclitaxel liposome with anti-HER-2 monoclonal antibodies as first-line salvage treatment of HER-2 positive advanced breast cancer based on the NATDSS

inclusion criteria:

1. Patients with unresectable or metastatic HER-2 positive breast cancer (immunohistochemistry 3+ or FISH positive) have received at least 2 cycles of salvage treatment with paclitaxel liposome in combination with anti-HER-2 therapy (monotherapy or dual-targeted therapy) ± other chemotherapy drugs (such as capecitabine, carboplatin, gemcitabine) as first-line treatment.
2. Patients with no visceral metastases, but only have bone metastases or multiple lymph node metastases are eligible for inclusion.
3. Eastern Cooperative Oncology Group (ECOG) performance status score of 0-2. Expected survival of at least 3 months.

exclusion criteria：

1. Accompanied by other secondary malignant tumors.
2. Male breast cancer or bilateral breast cancer.
3. brain metastasis

Patients with unresectable or metastatic HER-2 positive breast cancer (immunohistochemistry 3+ or FISH positive) have received at least 2 cycles of salvage treatment with paclitaxel liposome in combination with anti-HER-2 therapy (monotherapy or dual-targeted therapy) ± other chemotherapy drugs (such as capecitabine, carboplatin, gemcitabine) as first-line treatment.