The incidence of brain metastasis of Her2-negative breast cancer is high, which seriously affects the prognosis of patients.The treatment of brain metastasis of Her2-negative breast cancer is still tricky. The local efficacy of head radiotherapy for breast cancer brain metastases is remarkable, and systemic tumor progression in patients with brain metastases is the main reason for treatment failure. Sacituzumab Govitecan is the only Trop-2 antibody-coupled drug (ADC) approved for the treatment of unresectable locally advanced or metastatic Her2-negative breast cancer. However, the objective remission rate of Sacituzumab Govitecan for intracranial metastatic lesions has not been satisfactory. This study is an open, uncontrolled phase II clinical study to observe the efficacy and safety of Sacituzumab Govitecan combined with intracranial radiotherapy in the treatment of patients with brain metastases from Her2-negative breast cancer, in order to find a more effective treatment method.

This study is a single-arm open phase II clinical trial. It aims to observe the effectiveness and safety of Sacituzumab Govitecan combined with head radiotherapy in the treatment of Her2-negative breast cancer brain metastases, and to search for a more effective treatment option for Her2-negative breast cancer brain metastases. Patients were treated with Sacituzumab Govitecan 10mg/kg every 21 days as a treatment cycle, which was infused intravenously on day 1 and day 8, and the treatment was continued until the disease progressed or unacceptable toxicity occurred. Radiotherapy was administered after the second infusion of Sacituzumab Govitecan, on day 9 after the start of this regimen. The radiotherapy regimen was: brain metastases at a dose of 60 Gy/20 doses. For lesions located adjacent to the brainstem and optic nerve, 54 Gy/20 doses were given. For patients with ≥5 lesions, whole-brain radiotherapy at 40 Gy/20 doses was synchronized with radiotherapy to localized brain metastases.

Inclusion Criteria:

1. Have a definitive pathologic diagnosis of breast cancer with subtype Her2- (including IHC 0, IHC 1+ or IHC 2+ and ISH negative);
2. Have a measurable intracranial lesion;
3. Age ≥ 18 years;

Exclusion Criteria:

1. Patients with cerebrospinal membrane metastases;
2. Patients with acute/subacute hemorrhagic metastasis;
3. Inadequate organ function: 1) Blood tests: ANC ≤ 1.5 x 10^9/L, PLT ≤ 90 x 10^9/L, Hb ≤ 90g/L; 2) Blood biochemistry tests: TBIL ≥ 1.5 times the upper limit of normal; 3) ALT and AST ≥ 2.5 times the upper limit of normal;
4. Presence of serious and/or uncontrolled comorbidities that may affect participation: 1) allergy to study medications or adjuvant materials; 2) history of immunodeficiency, including HIV-positive or other acquired or congenital immunodeficiency diseases; 3) serious concomitant illnesses;
5. Pregnant and lactating female patients; female patients of childbearing age who are unwilling to use effective contraception during the trial period;
6. Patients who are unable to complete enhanced contrast MRI;
7. Patients who have been treated with Sacituzumab Govitecan and are resistant to the drug;
8. Any other condition that, in the opinion of the investigator, makes the patient ineligible for study participation.

All individual participant data that underlie results in a publication will be available to other researchers.

Starting 6 months after publication.

Individual participant data will be public accessable via contacting with principal investigator by email within 6 months after the trial complete.