How would you approach systemic management of a patient with an early aggressive metastatic relapse of previously early stage triple negative disease in breast only but now with multiple distant metastatic sites (including contralateral breast) which is now high ER expressing?

There isn't sufficient information to answer your question succinctly. Did she receive neoadjuvant chemotherapy, and, if so, how did she respond? Have you biopsied a metastatic site other than the contralateral breast? if not, you should, to assess its ER expression. Even if she is PD-L1 positive, the ER expression could impact her coverage for a trial of immunotherapy off study, but you may be able to find a study for which she is eligible. Assuming she is either PD-L1 negative or isn't a candidate for immunotherapy, if she is chemo naïve, I would start her on weekly paclitaxel and carboplatin (days 1, 8 and 15 every 28 days). If she's failed neoadjuvant chemotherapy this quickly, her prognosis is poor, but if her distant site is also ER-p...