Abstract
RATIONALE: Triple-negative breast cancer is characterized by a worse prognosis compared with other breast cancer subtypes, especially in the case of pretreated metastatic triple-negative breast cancer (mTNBC). Because of the limited treatment options and suboptimal response rates, there is a pressing need to explore novel treatment protocols. PATIENT CONCERNS: A 48-year-old female patient diagnosed with mTNBC who had not responded to multiple lines of therapy (including surgery, chemotherapy, and radiotherapy) but demonstrated significant efficacy and abscopal effects after enrolling in our clinical trial. DIAGNOSES: Triple-negative breast cancer with lung metastases. INTERVENTIONS: The clinical trial combined stereotactic body radiotherapy, immunotherapy, granulocyte-macrophage colony-stimulating factor, and thymosin alpha-1 to treat previously treated metastatic solid cancers. OUTCOMES: This combined treatment regimen implemented in this clinical trial yielded the patient's notable efficacy, accompanied by abscopal effects. The target lesion and the 3 observed lesions achieved a partial response according to the RECIST v1.1 criteria. reevaluation scans after 2 cycles of immunotherapy indicated a regression rate of -78.97% for the target lesion and -56.73% for the observed lesions. Hematological indexes were stable, and there was no apparent myelosuppression. Also, the tumor marker CA-199 exhibited a downward trend. During the course of treatment, the patient experienced a grade 2 skin reaction, which improved after receiving antiallergic treatment. No further adverse effects were observed. LESSONS: This treatment regimen may offer a promising treatment strategy for patients with mTNBC and other metastatic solid cancers.