Abstract
BackgroundSolitary plasmacytoma (SP) is a localized neoplastic plasma cell disorder with an annual incidence of less than 450 cases. Given the rarity of this disorder, it is difficult to conduct large-scale population studies. Consequently, very limited information on the disorder is available, making it difficult to estimate the incidence and survival rates. Furthermore, limited information is available on the efficacy of various treatment modalities in relation to primary tumor sites.MethodsThe data for this retrospective study were drawn from the Surveillance, Epidemiology and End Results (SEER) database, which comprises 18 registries; patient demographics, treatment modalities and survival rates were obtained for those diagnosed with SP from 1998 to 2007. Various prognostic factors were analyzed via Kaplan-Meier analysis and log-rank test, with 5-year relative survival rate defined as the primary outcome of interest. Cox regression analysis was employed in the multivariate analysis.ResultsThe SEER search from 1998 to 2007 yielded records for 1691 SP patients. The median age at diagnosis was 63 years. The patient cohort was 62.4% male, 37.6% female, 80% Caucasian, 14.6% African American and 5.4% other races. Additionally, 57.8% had osseous plasmacytoma, and 31.9% had extraosseous involvement. Unspecified plasmacytoma was noted in 10.2% of patients. The most common treatment modalities were radiotherapy (RT) (48.8%), followed by combination surgery with RT (21.2%) and surgery alone (11.6%). Univariate analysis of prognostic factors revealed that the survival outcomes were better for younger male patients who received RT with surgery (p < 0.05). Additionally, patients who received neoadjuvant RT had increased survival rates compared to those receiving adjuvant RT (86% vs 73%, p < 0.05). Furthermore, the analyses revealed that 5-year survival rates for patients with axial plasmacytoma were superior when RT was combined with surgery (p < 0.05). In the multivariate analysis, age <60 years and treatment with either RT or surgery showed superior survival rates. Progression to multiple myeloma (MM) was noted in 551 patients. Age >60 years was associated with a lower 5-year survival in patients who progressed to MM compared to those who were diagnosed initially with MM (15.1 vs 16.6%). Finally, those who received RT and progressed to MM still had a higher chance of survival than those who were diagnosed with MM initially and treated with RT/surgery (21.8% vs 15.9%, p < 0.05).ConclusionsA review of the pertinent literature indicates that we provided the most comprehensive population-based analysis of SP to date. Moreover, our study contributes to the establishment of the optimal SP treatment modality, as RT is the favored option in frontline settings. Consensus is currently lacking regarding the benefits of combined treatment including surgery. Thus, the findings reported here elucidate the role of primary treatment modalities while also demonstrating the quantifiable benefits of combining RT with surgery in relation to different primary tumor sites. While our results are promising, they should be confirmed through further large-scale randomized studies.
Highlights
Solitary plasmacytoma (SP) is a localized neoplastic plasma cell disorder with an annual incidence of less than 450 cases
These studies attempted to define the prognostic factors and establish appropriate treatment strategies, they were unsuccessful in identifying the key aspects that would delay the progression of the disease to MM
To meet the study objectives, we further assessed all identified patient records, in which we evaluated the SP according to primary tumor sites, focusing on bone (SPB, topography codes C40-41) and extramedullary sites (EMP, all topography codes excluding C40-41, C80) as the most common sites
Summary
Solitary plasmacytoma (SP) is a localized neoplastic plasma cell disorder with an annual incidence of less than 450 cases. Due to the low incidence of this disease, empirical evidence on the clinical course and benefits of various treatment modalities is scarce This limits the knowledge needed to determine the best course of action for individual SP patients. There is a paucity of published works on cases of SP, and most of those conducted to date have involved small cohorts, including approximately 50–250 patients [4,5,6,7,8] These studies attempted to define the prognostic factors and establish appropriate treatment strategies, they were unsuccessful in identifying the key aspects that would delay the progression of the disease to MM. Authors of other population-based studies evaluated either SBP or EMP in isolation, without conducting comparative analyses [10, 11]
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