Comparative Effectiveness of PAL Based-therapy as Initial ET Versus PAL Based-therapy After ChT for HR+/HER2- ABC

A multi-center non-interventional observational study led by the Cancer Hospital Chinese Academy of Medical Sciences to compare the effectiveness of palbociclib based-therapy as initial endocrine therapy versus palbociclib based-therapy after chemotherapy for HR+/HER2- advanced breast cancer.

This study is designed to be a multi-center non-interventional observational study led by the Cancer Hospital Chinese Academy of Medical Sciences. The target populations of this study are patients with HR+/HER2- advanced breast cancer who received palbociclib based-therapy as initial endocrine therapy or palbociclib based-therapy after chemotherapy from August 1, 2018 to December 31, 2023. It is expected to enroll 400 subjects in this study. The subjects' data such as demographics and other baseline characteristics, medications, prognosis, will be collected in a mixed manner, and statistical analysis of data will be conducted to compare the effectiveness outcome measures.

Eligibility Criteria:
Inclusion Criteria:

1. Age ≥ 18 years, female (retrospective part);
2. Histologically or cytologically confirmed recurrent or metastatic HR+/HER2- breast cancer, if there was metastatic pathology, the histological pathology of metastases should prevail (retrospective part);
3. Received palbociclib in combination with endocrine therapy as initial therapy in the first line and received at least 1 cycle; or received systemic chemotherapy in the first line followed by sequential palbociclib in combination with endocrine therapy and received at least 1 cycle (retrospective part);
4. The follow-up time was not less than 3 months after the initiation of palbociclib in combination with endocrine therapy (retrospective part);
5. Age ≥ 18 years, female (prospective part);
6. Histologically or cytologically confirmed recurrent or metastatic HR+/HER2- breast cancer, if there is metastatic pathology, the histological pathology of metastases should prevail (prospective part);
7. ECOG PS ≤ 2, and expected survival of more than half a year and no life-threatening visceral metastasis (prospective part);
8. Measurable disease (prospective part);
9. No or up to 1 regimen of chemotherapy for advanced breast cancer (prospective part);
10. The patient has good compliance, and needs to receive the treatment with the palbociclib-based therapy according to the condition (prospective part);
11. Normal function of major organs and hematopoietic function, i.e. meeting the following criteria: Blood cell count criteria should be in accordance with: (no blood transfusion and blood products, no G-CSF and other hematopoietic stimulating factors for correction in recent 14 days): Hemoglobin (HB) ≥ 80 g/L; Neutrophils (ANC) ≥ 1.5 × 10\^9/L; Platelet (PLT) ≥ 75 × 10\^9/L. Liver function, renal function and electrolytes meeting the following criteria: Total bilirubin (TBIL) \< 1.5 upper limit of normal (ULN), ≤ 3 ULN for patients with liver metastases; Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 3 ULN, and ≤ 5 ULN for patients with liver metastases; Serum Cr ≤ 1.5 ULN or endogenous creatinine clearance ≥ 60 ml/min (Cockcroft-Gault formula); Electrolytes: magnesium ≥ lower limit of normal (LLN) (prospective part);
12. The patient is compliant and voluntarily accepts the treatment, follow-up visit, laboratory examination and other study procedures according to the doctor's prescription (prospective part).

Exclusion Criteria:

1. ≥ 2 prior lines of chemotherapy for advanced breast cancer (retrospective part);
2. Treatment with other CDK4/6 inhibitors (abemaciclib or ribociclib) or endocrine therapy only (retrospective part);
3. Life-threatening visceral metastases, and lesions not evaluable for response (prospective part);
4. Neutrophils \< 1.5 × 10\^9/L; platelets \< 100 × 10\^9/L; not improved after medication (prospective part);
5. Total bilirubin ≥ 1.5 times the upper limit of normal, AST and ALT ≥ 2 times the upper limit of normal; serum Cr ≥ 1.5 times the upper limit of normal (prospective part);
6. Have central nervous system or meningeal invasion (prospective part);
7. Women who are pregnant, lactating, or planning to have children (prospective part);
8. Received ≥ 2 prior lines of chemotherapy for advanced breast cancer (prospective part);
9. Treatment with other CDK4/6 inhibitors (abemaciclib or ribociclib) or endocrine therapy only (prospective part);
10. Concomitant poorly controlled serious illness, major surgery, or history of other malignancy within 5 years (prospective part);
11. Other conditions that the investigator considers inappropriate for inclusion (prospective part).