What is your approach to treatment in hormone receptor positive, HER2 negative (0 IHC) metastatic breast cancer with ERBB2 gene amplification after progression on AI and fulvestrant CDK4/6i with visceral crisis?

More information will be helpful in approaching this case.

1. Was this a de novo presentation or a recurrence case?
2. Was the ERBB2 IHC done on the primary tumor or a metastatic lesion?
3. Was the ERBB2 amplification detected in tissue (primary or metastatic)? At what point in time was this tested (upon ...