Plasmacytoma of bone, extramedullary plasmacytoma, and multiple myeloma: incidence and survival in the United States, 1992–2004

Population‐based plasmacytoma incidence and survival data are sparse. We analyzed incidence rates (IRs), IR ratios (IRRs), and 5‐year relative survival for plasmacytoma overall and by site – bone (P‐bone) and extramedullary (P‐extramedullary) – in the Surveillance, Epidemiology and End Results (SEER) Program (1992–2004). For comparison, we included cases of multiple myeloma (MM) diagnosed over the same time period in SEER. Incidence of MM (n = 23 544; IR 5·35/100 000 person‐years) was 16‐times higher than plasmacytoma overall (n = 1543; IR = 0·34), and incidence of P‐bone was 40% higher than P‐extramedullary (P < 0·0001). The male‐to‐female IRRs for P‐bone, P‐extramedullary, and MM were 2·0, 2·6, and 1·5, respectively. For plasmacytoma and MM, IRs were highest in Blacks, intermediate in Whites, and lowest in Asian/Pacific Islanders. Compared with Whites, the Black IR was ∼30% higher for P‐extramedullary and P‐bone and 120% higher for MM. IRs for all neoplasms increased exponentially with advancing age, less prominently at older ages for plasmacytoma than MM. Distinct age, gender, and race incidence patterns of plasma cell disorders suggest underlying differences in clinical detection, susceptibility, disease biology and/or aetiological heterogeneity. Five‐year relative survival for P‐bone, P‐extramedullary, and MM varied significantly by age (<60/60+ years), supporting age‐related differences in disease burden at presentation, disease biology, and/or treatment approaches.