How do you approach the timing / feasibility of CD38 re-treatment (daratumumab or isatuximab) in a previously CD38-refractory patient with myeloma?  

For example: do you set a time threshold, for example 12 months since the last dose of CD38 mAb will suffice? Do you look at NK cell subsetting (i.e. CD56)? If a bone marrow biopsy were performed, would you look at CD38 expression on the myeloma cells by flow cytometry to gauge whether CD38 re-treatment might work?