How do you treat metastatic breast cancer which is HR positive, Her2 negative with PIK3CA+ and high tumor mutational burden (>10) who progressed after prior ET+CDK 4/6 and PIK3CA inhibitor therapy?

I will take an initial stab at this, but I know there are varying thoughts from other clinicians and I'm always interested to learn how others think through this.

To start, I'm guessing that you're asking about immunotherapy here, and when you might consider using it. Unfortunately, these patients ha...