Individualize management for advanced breast cancer with pyrotinib-based anti-HER2 therapy: a case report.

Background: We report a case of metastatic human epidermal growth factor receptor-2 (HER2) positive breast cancer who achieved encouraging clinical benefits across multiple pyrotinib-based anti-HER2 therapies. Case Description: A 33-year-old woman was diagnosed with hormone receptor (HR) positive, HER2-positive breast cancer in June 2018, and did not receive adjuvant radiotherapy, chemotherapy, or anti-HER2 targeted therapy post-breast conserving surgery. By May 2020, she developed recurrence of the left breast mass with metastases in liver, bone and lymph nodes. She then received pyrotinib plus trastuzumab and nab-paclitaxel as first-line therapy. Both the left breast mass and liver metastases showed noticeable improvement, with the disease evaluated as partial response (PR). Despite this promising result, the patient developed brain metastases after first-line treatment. A combination regimen of pyrotinib retention plus inetetamab and vinorelbine were administered as second-line anti-HER2 therapy, and the brain metastases visibly shrunk, leading to PR, with the extracranial lesions remaining stable. Ultimately, due to brain lesions progression, the treatment was transitioned to trastuzumab deruxtecan. We applied next generation sequencing (NGS) to illustrate the efficacy of anti-HER2 therapy and minimal residual disease (MRD) to detect the disease status. Conclusions: Pyrotinib is a promising antineoplastic agent for HER2-positive advanced breast cancer patients. Under the guidance of precision medicine, it is encouraged to utilize novel diagnostic and therapeutic methods to manage advanced breast cancer patients.