No correlation between the percent change in the monoclonal protein and in i-DPD in 20 MM patients receiving chemotherapy. (•) Patients who improved on chemotherapy, with a decrease in the monoclonal protein of ≥25% of the pretreatment level. (E) Patient no. E, who showed a decrease in the monoclonal component to 35% of the pretreatment concentration after 10 months of chemotherapy. i-DPD remained nearly unchanged (91% of the pretreatment value). (F) Patient no. F, who presented with an increase in the monoclonal protein to 110% of the initial value (after 5 months of treatment) but also showed a concomitant decrease in i-DPD to 8.3% of the baseline level.