How (and when) is primary refractory AL amyloidosis defined following D-CyBorD treatment? Is there a threshold of biomarker reduction following 1-2 cycles that, if not met, should prompt early consideration of treatment change?

Two previous questions have discussed treatment options if a CR is not achieved after 6 cycles of D-CyBorD. Would you wait until 6 cycles? Is there a biomarker threshold for the first 1-2 cycles that, if not met, would prompt you to change therapy earlier? If so, to what?