Would you consider chemoimmunotherapy in a patient with hormone positive breast cancer treated with chemotherapy who has progressed to triple negative breast cancer?

If the patient had treated ER+ early stage disease and the metastatic recurrence was retested to be TNBC and CPS>=10, I would treat using the KY355 regimens in the 1st line setting.

If you are asking about ER+ metastatic disease that was treated as such then rebiopsied later on at progression and declared TNBC, then you probably have disease heterogeneity coming into play. This would be off label but if the biopsy did have a CPS of 10 or more, I would consider trying to add it to 1st line chemotherapy when you start it.