The Role of CD56 as an Immunophenotypic Marker in the Clinical Course of Multiple Myeloma

Background: CD56 expression has been proposed as a prognostic and predictive biomarker in multiple myeloma. However, its clinical relevance in the context of modern induction therapy and autologous stem cell transplantation (ASCT) remains controversial. Methods: The researchers studied individuals with newly diagnosed multiple myeloma. CD56 expression was assessed by flow cytometry at diagnosis. Assessment was performed to determine patients' responses to induction therapy and to measure their progression-free and overall survival rates. Results: The study included 88 participants, of whom 68 (77%) were CD56-positive, and 20 (23%) were CD56-negative. The study results showed that CD56(-) patients developed plasmacytomas at a 70% rate, while CD56(+) patients had a 46% rate (p = 0.055). A similar pattern was observed for extramedullary lesions (p = 0.006). The induction response rate was lower in CD56-negative patients than in CD56-positive patients (65% vs. 85%, p = 0.043). Patients who did not experience relapse received more CD34⁺ cells (11.9 ± 5.71 vs. 9.29 ± 2.57 × 10⁶/kg, p = 0.012) and had higher post-transplant response rates (91% vs. 63%, p = 0.002). The patients who received induction treatment before their disease showed better survival outcomes than patients who did not respond to treatment (90.2% vs. 87.1%, p = 0.029) and patients who did not experience relapse (92.7% vs. 85.0%, p = 0.022). CD56 status did not affect survival outcomes. Conclusions: CD56 expression is associated with disease burden and response to induction therapy in multiple myeloma, supporting its role as an early disease-modifying factor. However, its prognostic value appears limited in patients receiving high-dose chemotherapy with ASCT, suggesting that intensive treatment may mitigate the adverse impact of CD56 negativity.