PFS according to lenalidomide (Len) duration, IMiD-free interval, and last Len dose. (A) PFS according to a Len duration <12 months (blue line) or ≥12 months (red line). (B) PFS according to an IMiD-free interval <18 months (blue line) or ≥18 months (red line). (C) PFS according to last Len dose (5-15 mg) (blue line) vs 25 mg (red line).