Kinetics of paraprotein clearance after autografting for multiple myeloma

The kinetics of paraprotein clearance after autografting for multiple myeloma have not been described. We studied 33 myeloma patients in plateau phase with detectable paraprotein (3-34 milligrams, median 10 milligrams) at the time of ABMT who received melphalan (200 mg/m2) and methylprednisolone (1.5 g x 5) for conditioning. Fifteen patients received interferon-alpha post-transplant as part of a randomized study. Twenty-four of 33 (72.7%) patients eventually cleared the paraprotein at a median of 47 days (range 5-783) post-transplant. The probability of clearance was lower (46.7 vs 94.4%, P = 0.004) and the time taken to clear paraprotein longer (142 vs 29 days, P = 0.003) in patients with a higher level (> 10 milligrams) at the time of the transplant. However, clearance occurred within 6 months in 23 of 24 (95.8%) patients who ultimately cleared the paraprotein. Interferon-alpha did not influence the clearance of paraprotein. We conclude that after autografting for myeloma, the time taken to clear paraprotein is longer and the probability of clearance lower with higher levels at the time of ABMT, and most patients who eventually clear the paraprotein do so within 6 months. Because the probability of clearing paraprotein (and thus attaining remission) in patients with detectable paraprotein 6 months post-transplant is low, a decision about further treatment may be made at this point.