How would you manage an elderly patient with a history of stage I CLL and newly diagnosed metastatic ER+/HER2+ breast cancer?

The focus would be on the diagnosis which seems most likely to be life-limiting and/or a source of morbidity. Although there aren't many details here regarding the metastatic ER+ HER2+ breast cancer (e.g. where are the mets? Bone? Liver? Are there symptoms?) one presumes that this is more life-limiting than a Stage I CLL. As such, I would aim to treat her HER2+ metastatic breast cancer as her health allows. Additional details about this patient's co-morbidities are missing, but most patients can tolerate weekly paclitaxel plus dual HER2-targeted therapy. I would start with this therapy with a goal of 4-6 cycles if responding (ala CLEOPATRA) and then try to transition to an endocrine therapy + HER2 targeted therapy.