Long‑term progression‑free survival in HR+/HER2+ advanced breast cancer with combination therapy with a CDK4/6 inhibitor and first‑line maintenance therapy: A case report.

Abstract

The current standard treatment for hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-positive advanced breast cancer (BC) involves the use of anti-HER2 monoclonal antibodies combined with chemotherapy, followed by sequential endocrine therapy. However, crosstalk between the HR and HER2 pathways may cause drug resistance. Combining therapies targeting both the HR and HER2 pathways may be a rational approach for patients with HR⁺/HER2⁺ tumors, as this strategy could counteract resistance by blocking crosstalk in the receptor pathway. However, clinical data in this field remain limited. The present report describes the case of a patient with HR⁺/HER2⁺ late-stage BC who achieved a long-term partial response rate after receiving anti-HER2 combination chemotherapy followed by sequential treatment with endocrine therapy and cyclin-dependent kinase 4/6 (CDK4/6) inhibitors. The present case provides additional evidence suggesting that incorporating CDK4/6 inhibitors into standard targeted chemotherapy regimens may be an effective treatment option for patients with HR⁺/HER2⁺ BC.