Prognostic Relevance of CD56 Expression in Patients with Multiple Myeloma Treated with High-Dose Melphalan-Based Chemotherapy and Autologous Stem Cell Transplant.

CD56 is a neural adhesion molecule and expressed in 70–80% cases of multiple myeloma (MM). Lack of CD56 expression has shown to be a poor prognosis in MM patients treated with conventional chemotherapy, but its prognostic relevance in MM treated with high dose chemotherapy and autologous stem cell transplant (ASCT) is not known. CD56 expression was evaluated by immunohistochemistry on bone marrow paraffin embed specimens from 107 MM cases undergoing Melphalan-based high dose therapy and ASCT. The 66 men and 41 women had a median age of 54 years. 53 patients had an IgG paraprotein, 30 IgA, 4 IgD, 15 light chain disease and 5 were nonsecretory. The median post-transplant follow-up was 20 months. Of 107 MM patients, 76 (71%) were CD56 positive and 31 negative. 27 died during the follow-up period including 7(23%) in CD56 negative and 20 (26%) in CD56 positive group; 50 were in relapse including 11 (35%) in CD56-negative, and 39 (51%) in CD56 positive group. The median overall survival for the CD56 positive patients was 48.1 months and for the CD56 negative patients, 44.8 months (p=0.67). The median progression free survival of the CD56 positive patients was 25.8 months and for the CD56 negative patients, 33.1 months (p=0.28). CD56 negative myeloma was associated with bone lesions (69% for CD56 positive vs 90% for CD56 negative group, p=0.032). However, CD56 was not associated with other biological factors including age, sex, hemoglobin, calcium, albumin, c-reactive protein, beta-2 microglobulin, immunoglobulin isotype, stage of the disease or bone marrow plasmacytosis. Furthermore, there was no correlation between CD56 expression and genetic aberrations including deletions of 13q14, 17p13.1 (p53), translocations t(11;14) or t(4;14) as evaluated by fluorescence in situ hybridization (FISH). In contrast to reports of CD56 in myeloma treated with conventional chemotherapy, we found CD56 negativity does not confer a poor prognosis in our patients, suggesting Melphalan-based high-dose chemotherapy and ASCT may overcome the adverse influence of CD56 negative myeloma.