P1-19-1DETECTION OF MINIMAL RESIDUAL DISEASE IN AUTOGRAFTS BY ASO-PCR FOR PATIENTS WITH MULTIPLE MYELOMA

Abstract Background: The high-dose melphalan followed by autologous blood stem cell transplantation (ASCT) is a standard treatment for younger patients with multiple myeloma (MM). Recent reports have shown that achieving molecular complete response is associated with longer progression-free survival. However, the impact of minimal residual disease (MRD) in peripheral blood cell autografts on outcome remains unknown. We report the clinical and molecular follow-up of 6 MM patients who underwent ASCT. Methods: Six patients in whom the treatment was performed at Iwate Medical University Hospital and MRD in autografts was evaluable were included in the study. All patients had achieved at least a partial response after ASCT. Fresh bone marrow cells at diagnosis as well as autografts were obtained for DNA extraction. The CDR III coding region of the IgH gene was studied by direct sequencing of PCR product from bone marrow samples at diagnosis, and then MRD in each autograft was measured by ASO-PCR. Results: Four of 6 patients are alive: 2 who had no MRD in their autografts maintain a stringent complete response (CR) for 40 and 8 months after ASCT, while 2 who had MRD in them have serum M protein assessable by immunofixation for 20 and 10 months after ASCT. Two patients died from disease progression, both of which had MRD in their autografts and had have serum M protein after ASCT. Conclusion: These observations suggest that no MRD in peripheral blood cell autografts may be associated with a durable CR after ASCT. In addition, the post-ASCT treatment such as consolidation or maintenance therapy should be considered for MM patients who have MRD in autografts. Larger study and serial follow-up should be recommended to establish the clinical impact of MRD measurement in autografts in MM patients. As of writing, follow-up MRD analyses for total 13 MM patients are ongoing. Updated results will be presented.