What is your approach to pRBC transfusion support for myeloma-related anemia?

There is likely not a single right answer to this.

The data suggests that a hemoglobin threshold of 7 g/dL is reasonable for critically ill patients rather than a higher threshold. The Clinical Practice Guidelines From the AABB recommend a threshold of 7-8 g/dL.

In general, I follow these rules:

1. Transfuse to hgb goal of 8 g/dL.
2. If still symptomatic from anemia, consider alternative therapy options to boost hemoglobin. For instance, can you use erythropoietin stimulating agents? The joint ASCO/ASH...

For myeloma-related anemia, I tend to have a restrictive RBC transfusion threshold (Hb 7-8).

I use ESAs for chemotherapy-associated anemia when I can't dose reduce (e.g. monoclonal antibodies) or when drug dose is tied to efficacy and the patient is just getting started, e.g. proteasome inhibitors or selinexor. I prefer to dose reduce IMiDs since there is no dose response curve for lenalidomide ≥ 10 mg or pomalidomide ≥ 2 mg.

For patients with significant CKD (eGFR < 20 mL/min) whether on trea...

Very little that I'd add to the excellent answers by @Dr. First Last and @Dr. First Last above. I will add that, when Hgb is disproportionately low compared to % plasma cells in the bone marrow, I suspect that inflammatory cytokines within the tumor microenvironment are driving the anemia more so than crowding out of RBC precursors per se.

Those same inflammatory cytokines are also making patients feel fatigued, and I'm not sure that transfusing pRBCs (beyond a goal of 7 or rarely of 8, as not...