Comparison of clinical characteristics, treatment efficacy and survival in patients with newly diagnosed multiple myeloma with single- versus multi-site extramedullary invasion

Purpose: We aimed to compare the clinical characteristics, treatment efficacy and survival in patients with newly diagnosed multiple myeloma with single- versus multi-site extramedullary invasion.

Methods: A total of 90 extramedullary multiple myeloma (EMM) patients were included. We compared the characteristics, overall remission rates (ORRs) and survival among patients with single-site and multi-site invasions. Comparison was also done regarding extramedullary-bone-related (EM-B) and extramedullary-extraosseous (EM-E) multiple myeloma patients.

Results: Patients with multi-site invasion had higher LDH (179.0 U/L) than single-site invasion (P = 0.016). Significantly higher LDH was also showed in patients with EM-E (189.4 U/L) than EM-B (P = 0.025). The ORR of patients with single-site invasion (72.1%) was not significantly higher than multi-site invasion (68.2%) (P = 0.690). But the ORR of patients with EM-B was significantly higher than EM-E (78.2 vs. 56.3%, P = 0.031). Among patients with single-site invasion, the multivariate survival analysis showed that PI plus IMiD regimen significantly improved the PFS (P < 0.05). Among patients with multi-site invasion or with EM-B, the multivariate survival analysis confirmed the associations of rISS III with poor PFS and OS (P < 0.05). Among patients with EM-E, plasma cell percentage ≥ 20% was associated with significantly poor PFS and OS (P < 0.05).

Conclusion: rISS stage III was possibly associated with poor survival of EMM patients with multi-site invasion or with EM-B. Plasma cell percentage ≥ 20% was associated with poor survival of EMM patients with EM-E. Comparison should not only be done between single- and multi-site invasions, but also between EM-B and EM-E.