What would you use as adjuvant endocrine therapy for a patient who developed an invasive, hormone receptor positive breast cancer while on raloxifene for almost a decade prior?  

In this situation I would use an aromatase inhibitor if possible. One would not expect an ESR1 activating mutation to be readily detected after treatment with a SERM, since estrogen deprivation rather than receptor blockade enriches for ESR1 mutant clones.