Survival trends and prognostic factors in patients with solitary plasmacytoma of bone: A population-based study

Solitary plasmacytoma of bone (SPB) is a single, isolated plasmacytoma originated from the bone. The survival trends of patients with SPB in recent years remain unknown. And the prognostic system of SPB may also need to be refined. The 18 Surveillance, Epidemiology, and End Results (SEER) databases of the National Cancer Institute in the United States were used to extract data for this study. The third edition of the International Classification of Disease for Oncology (ICD-O-3) code 9731 was used to identify cases of SPB. For each case, factors including age at the time of diagnosis, sex, race, marital status, insurance status, primary sites of tumors, and the use of surgery were collected. The outcomes of patients with SPB were compared between two groups. And the prognostic impacts of baseline characteristics and use of surgery was studied. A total of 4103 (from 1976 to 2016) cases of SPB were identified. The median age was 65 years old. Patients in time period-2 (2008-2016) show better survival as compared to those in time period-1(1976-2007) (median overall survival: 88 months vs. 73 months, p = 0.0332). Age ≤ 65 years and being male were associated with better outcomes. The widowed individuals had significantly inferior survival and myeloma-specific survival than the single, married, or divorced individuals (p values all <0.0001). Patients with lesions in bones of skull and face and associated joints had longer survival as compared with those with bone lesions in other sites (median overall survival: 107 months vs. 79 months, p = 0.0694). The use of surgery was significantly associated with improved survival (median survival: surgery performed 98 months vs. not performed 73 months, hazards ratio [HR]: 0.7623, 95% CI: 0.7009-0.8472; p < 0.0001) and myeloma-specific survival (median myeloma-specific survival: surgery 160.0 months vs. no surgery 143.0 months, HR: 0.8469, 95% CI: 0.7493-0.9572; p = 0.0078). Multivariable analysis revealed that surgery, marital status, and age were independent prognostic factors for overall survival in patients with SPB. The improvement in the survival of patients with SPB has been observed in recent years. And several potential prognostic factors were identified. Future prospective studies are warranted to explore the roles of novel agents, surgery, and systemic chemotherapy in the treatment of SPB.