A population-based study on incidence trends of myeloma in the United States over 2000-2020.

Myeloma is one of the most common types of haematological malignancies. We aimed to investigate the incidence rates of myeloma by sex, race, age, and histological subgroups in the United States (US) over 2000-2020. Data were retrieved from the the Surveillance, Epidemiology, and End Results (SEER) 22 database. The International Classification of Diseases for Oncology version 3 morphological codes 9731, 9732, and 9734 were assigned for solitary plasmacytoma of bone, plasma cell myeloma, and extraosseous plasmacytoma, respectively. Average annual percent change (AAPC) and the pairwise comparison with the parallelism and coincidence were reported. All estimates were reported as counts and age-adjusted incidence rates per 100,000 individuals. Over 2000-2019, most of myeloma cases were among those aged at least 55 years (85.51%), men (54.82%), and non-Hispanic Whites (66.67%). Among different subtypes, plasma cell myeloma with 193,530 cases had the highest frequency over the same period. Also, there was a significant decrease in the age-standardized incidence rate of myeloma across all races/ethnicities in both sexes within all age groups (AAPC: - 8.02; 95% confidence interval (CI): - 10.43 to - 5.61) and those aged < 55 (AAPC: - 8.64; 95% CI - 11.02 to - 6.25) from 2019 to November 2020. The overall trends of myeloma incidence rates were not parallel, nor identical. There was an increase in myeloma incidence in both sexes, with a highly increasing rate, particularly among younger Hispanic and non-Hispanic Black women over 2000-2019. However, a remarkable decline was observed in the incidence rates following the COVID-19 pandemic in 2020.

Epidemiology and survival of primary extraosseous plasmacytoma: insights from a population-based study with a 20-year follow-up.

Primary extraosseous plasmacytoma (PEP) is a rare and localized form of plasmacytoma that is not well understood. This study aimed to investigate the clinical features and prognostic factors associated with PEP. Using the Surveillance, Epidemiology, and End Results (SEER) database, a total of 1044 patients diagnosed with PEP between 2000 and 2019 were identified. The average age was 60.3 ± 15.2 years, with 64.3% being male (male: female = 1.8:1) and 53.8% being over 60-year old. The survival outcome of patients with PEP depends on several factors including age, race, marital status, and treatment options such as chemotherapy, radiotherapy, and surgery, which were also identified as independent predictors of overall survival for PEP. Patients who were younger, Asian or Pacific Islander, American Indian or Native American, and received radiotherapy or surgery had a more favorable prognosis, while those who underwent chemotherapy had poorer outcomes.

Pediatric Plasma Cell Neoplasms: A Population-Based Study.

INTRODUCTION: Plasma cell neoplasms are exceptionally rare in the pediatric population; the demographic characteristics and the clinical outcomes of plasma cell neoplasms in this population are currently poorly understood. The aim of this study was to provide a comprehensive analysis of pediatric plasma cell neoplasms, based on the United-States Surveillance, Epidemiology, and End Results (SEER) program registries. MATERIALS AND METHODS: All pediatric patients (aged less than 20 years) diagnosed with a malignant plasma cell neoplasm were retrieved from the SEER Program database (18 registries), collecting patient records between 2000 and 2018. The plasma cell neoplasm type, sex, age at diagnosis, year of diagnosis, race and origin, primary disease site, follow-up duration, and vital status at the last known contact were retrieved and analyzed. RESULTS: The age-adjusted incidence rate of plasma cell neoplasms for 1,000,000 person-years was 0.06 for the pediatric population (compared with 90.6 for the adult population). The types of pediatric plasma cell neoplasms predominantly consisted of plasmacytomas, with 11 solitary extraosseous plasmacytoma (42.3%) and 7 solitary bone plasmacytoma (26.9%), while plasma cell myelomas represented only a minority of the neoplasms (8 patients; 30.8%). Most plasmacytomas were localized in the head and neck region. Hispanic patients represented 50% of the pediatric plasma cell neoplasm cases (but only 11.1% of adult cases, P < .01). Female-to-Male ratio was 1.36. Five-year overall survival rates were 88.2% (95% confidence interval [95% CI]: 74.2%-100%) for pediatric plasmacytoma and 36.5% (95% CI: 12.4%-100%) for pediatric plasma cell myeloma (P = .013). CONCLUSION: This first population-based study of pediatric plasma cell neoplasms underlines the rarity of this entity and demonstrates its unique characteristics, including the significant predominance of plasmacytomas, of female patients, and of patients from hispanic origin, and the poor clinical outcomes of pediatric plasma cell myeloma patients.

Clinical presentation and outcomes of solitary plasmacytoma in a tertiary hospital in the UK.

Solitary plasmacytoma is a rare localised neoplasm of monoclonal plasma cells. The standard treatment involves radical radiotherapy; however, a significant proportion of patients subsequently develop multiple myeloma. In this study, we evaluate the outcomes of solitary plasmacytoma in a retrospective cohort of patients treated in a single tertiary centre.The case records of plasmacytoma patients treated in a 15-year period were analysed and retrospectively followed up from the date of diagnosis. Thirty-four cases met the inclusion criteria; 27 (79%) solitary plasmacytoma of bone (SBP) and 7 (21%) extramedullary plasmacytoma (EMP). The thoracic vertebrae were the commonest sites for SBP while EMP occurred most frequently in the upper airway. Pain and spinal cord compression were the most frequent symptoms. A paraprotein was detectable in 18 (53%) patients. Over a median follow-up of 48 months, 13 (38%) developed multiple myeloma. The 5- and 10-year survival rates were 80% and 56%, respectively; median progression-free survival was 77 months. Four patients (12%) developed a second malignancy.Progression to multiple myeloma remains a formidable challenge in the management of solitary plasmacytoma, hence adjunct therapies are needed.

Retrospective analysis of plasmacytoma in Kansai Myeloma Forum Registry.

We retrospectively analyzed 51 patients with solitary plasmacytoma diagnosed from October 2002 to September 2018 from a cohort of 3575 patients with plasma cell dyscrasias registered in the Kansai Myeloma Forum. Twenty-seven patients had solitary bone plasmacytoma (SBP) and 24 had extramedullary plasmacytoma (EMP), with prevalence of 0.8% and 0.7%, respectively. The most frequent M protein was IgG (40%) in SBP, whereas non-secretory proteins were most frequent (50%) in EMP. Five-year overall survival was 78.2% in SBP and 80.8% in EMP (P = 0.894). Among patients with SBP, 44% progressed to MM with a median time of 10.5 months (2.4-93.3 months), whereas 8% of EMP patients progressed to MM with a median time of 18.6 months (13.0-24.2 months). The most frequent treatment was radiotherapy (41%) or observation (41%) in SBP, and chemotherapy (54%) in EMP. No statistically significant difference was observed upon univariate analysis of prognostic factors including age, sex, performance status, and IgG M protein. Our results suggest that there are biological differences between SBP and EMP in real-world settings.

[Prevalence investigation of solitary plasmacytoma in China: A calculation based on national urban medical insurance in 2016].

Objective: The aim of this study is to analyze the distribution features of patients with solitary plasmacytoma and calculate the prevalence of solitary plasmacytoma in China in the year 2016. Methods: This study was based on China's urban employees' basic medical insurance and the urban residences' basic medical insurance from 21 provinces from January 1, 2016 to December 31, 2016. Patients with solitary plasmacytoma were identified by disease names and codes. Subgroup analyses were carried out by sex, region, and age. Furthermore, sensitivity analyses were performed to test the robustness of the results. Age-adjusted prevalence was calculated based on the 2010 Chinese census data, the 2013 Revised European Standard Population, the 2010 US population, and the 2011 Australian population. Results: In 2016, the prevalence of solitary plasmacytoma in China was 1.18 per 100 000 population (95%CI, 1.06-1.31) , with 1.26 per 100 000 population (95% CI, 1.10-1.43) and 1.10 per 100 000 population (95% CI, 0.93-1.29) for males and females, respectively. The age-adjusted prevalence based on the 2010 Chinese census data was 0.85 per 100 000 population (95% CI, 0.82-0.88) . Conclusion: This study estimated the prevalence of solitary plasmacytoma in China on the basis of the national urban medical insurance, which can provide clues for the enactment of solitary plasmacytoma-related medical policies and basic studies about solitary plasmacytoma.

Population-based study of patients with primary Sjögren's syndrome and lymphoma: lymphoma subtypes, clinical characteristics, and gender differences.

Objective: To examine lymphoma subtypes, clinical characteristics, and gender differences in patients with primary Sjögren's syndrome (pSS) and lymphoma in a population-based setting.Method: Patients with Sjögren's syndrome and lymphoma diagnoses were identified by linkage of the Swedish Patient Register 1964-2007 with the Cancer Register 1990-2007. Clinical data were collected from medical records and lymphoma tissues were re-examined. The lymphoma subtype distribution was compared with the Swedish Lymphoma Register.Results: We identified 105 pSS patients with lymphoma. Diffuse large B-cell lymphoma (DLBCL) (32%) and marginal zone lymphoma [MZL including mucosa-associated lymphoid tissue (MALT) lymphoma] (31%) were the most common lymphoma subtypes. The proportion of DLBCL was not increased compared to the general population reference (32%, p = 1), in contrast to MZL (general population 5%, p < 0.0001). Compared to DLBCL, MALT lymphoma was diagnosed at a younger age (55 vs 67 years, p = 0.0001), and earlier after patient-reported sicca onset (7 vs 18 years, p = 0.0001) and pSS diagnosis (2 vs 9 years, p = 0.0005). Sixteen of the pSS-lymphoma cases were men (15%), twice the proportion in general pSS populations. Compared to women, men had a shorter median time from pSS diagnosis to lymphoma diagnosis (1 vs 8 years, p = 0.0003) and more often had lymphoma in the salivary glands (56% vs 29%, p = 0.04).Conclusion: DLBCL and MZL are common in pSS patients, but only MZL/MALT lymphoma occurs at an increased relative frequency in pSS compared to the general population. The study supports increased awareness of signs of lymphoma in men in the first years after pSS diagnosis.

Clinical Features of Head and Neck Solitary Extramedullary Plasmacytoma in Taiwan.

BACKGROUND/AIM: Solitary extramedullary plasmacytoma (SEP) is a rare, malignant plasma-cell tumor, which mainly occurs in the head and neck regions. Globally the disease has been rarely happening up to 2019, with only about ten papers focused on SEP cases reported in English. Thus, a literature collectively reviewing the characteristics of the patients would be valuable. PATIENTS AND METHODS: We enrolled 10 SEP patients, and recorded their primary sites and the treatment modality, and analyzed their survival rates and outcomes. We also reviewed previous studies and compared their findings with ours. RESULTS: No gender or age disparity has been observed, and younger patients had a better local control with RT compared to surgery among our patients. CONCLUSION: Further investigations with more patients and long-time follow-up may provide more information for treatment determination and the recurrence and progression from SEP to MM.

Clinicopathological spectrum of solitary Plasmacytoma: a single center experience from coastal India.

BACKGROUND: Plasma cell disorders are a rare group of hematological malignancies that accounts for 10% of all hematological neoplasms. Solitary plasmacytomas are rarer entities accounting for less than 5% of all the plasma cell dyscrasias. They encompass three subtypes - Solitary Plasmacytoma of Bone (SPB) and Solitary Extramedullary Plasmacytoma (SEP) and multiple solitary plasmacytomas (MSP). In this study, we discuss the clinical, histopathological and immunohistochemical characteristics of solitary plasmacytomas. METHODS: A 13 year retrospective analysis of solitary plasmacytomas was performed from a single tertiary care center. Bone marrow evaluation was done concurrently at the time of diagnosis to rule out the presence of multiple myeloma. RESULTS: A total of 29 cases fulfilled the diagnostic criteria for SP during the study period. SPB accounted for 55.2%, SEP for 44.4% and MSP for 3.4% of the cases. The most common sites involved were the paranasal sinuses and vertebrae. Other infrequent sites included lymph node, tonsil and lungs. The mean age of presentation of SPB was a decade later than SEP. A male preponderance was observed in both subtypes. CONCLUSION: Solitary plasmacytoma is a rare entity, the diagnosis of which requires a systematic approach. There is limited data available in the literature on the clinico-pathological characteristics of SP from India.

Long-term clinical outcomes in a cohort of patients with solitary plasmacytoma treated in the modern era.

BACKGROUND: The risk of recurrence of solitary plasmacytoma (SP)/progression to MM is well established, but patient, imaging and treatment factors influencing risk of progression require further evaluation. METHODS: This is a retrospective analysis of 66 SP patients (23 UK, 43 Brazil) diagnosed 1989-2016. Patient baseline characteristics were recorded. The incidence of progression to MM was calculated, including biochemical and imaging findings and the treatment modality received. Survival estimates were determined by Kaplan-Meier analyses. RESULTS: With a median follow-up of 53.6 months the 5 year overall survival (OS) was 90.7% (95%CI 79-96%). The median progression free survival (PFS) from diagnosis was 61 months. Cumulative incidence of progression to MM was 49.9% at 5 years (95% CI 35.6-62.6%) and was significantly higher with bone plasmacytoma (47.2%, 95%CI 31.9-61.1%), than an extramedullary location (8.3%, 95%CI 0.4-32.3%, Gray test p = 0.0095)). The majority of patients with solitary bony plasmacytoma (SBP) received radiotherapy (RT) (51/53, 96.2%) whereas most extramedullary cases were treated with surgical resection (7/13, 53.8%). A small proportion of SBP patients received additional upfront chemotherapy, with 5/6 in remission after a median follow-up (FU) of 10 years. The diagnostic yield of surveillance functional FU imaging without other indications of relapse/progression was low. The positive predictive value of functional FU imaging was high but with a low negative predictive value, especially in cases of suspected relapse/progression. CONCLUSION: Our data suggests functional imaging should be used if clinical suspicion of relapse/progression, rather than a routine surveillance tool, and upfront adjuvant chemotherapy is worthy of prospective evaluation.

Clinical features, radiological profiles, and surgical outcomes of primary intracranial solitary plasmacytomas: a report of 17 cases and a pooled analysis of individual patient data.

PURPOSE: We aim to delineate the clinical characteristics of patients with primary intracranial solitary plasmacytoma (PISPC) and prognostic factors for their outcomes. METHODS: This study retrospectively reviewed 17 patients with PISPC from our center and an additional 70 cases of PISPC published previously to analyze outcome predictors. RESULTS: The entire cohort included 38 (43.7%) males and 49 (56.3%) females with a mean age of 54 years. Skull base tumors were found in 49 (56.3%) patients. Gross total resection (GTR) was achieved in 31 (35.6%) patients. Postoperative adjuvant treatments, including radiotherapy (RT) alone, chemotherapy (CMT) alone, and RT + CMT were administered in 49 (56.3%) patients, 3 (3.5%) patients, and 16 (18.4%) patients, respectively. After a median follow-up of 24 (mean 42.4) months, the 5-year disease progression-free survival (PFS), recurrence-free survival (RFS), multiple myeloma (MM)-free survival (MMFS), and overall survival (OS) were 52.9%, 76.2%, 69.6%, and 76.1%, respectively. Multivariate analysis unveiled that a skull base tumor location (HR 2.395, p = 0.040) and no RT (HR 3.115, p = 0.004) were negative prognostic factors for PFS, no RT (HR 10.526, p = 0.003) for RFS, each 1-year increase in age (HR 1.039, p = 0.049) for MMFS, and increasing age (HR 1.052, p = 0.043) and CMT (HR 6.022, p = 0.005) were risk factors for OS. However, GTR did not benefit the aforementioned outcomes. CONCLUSION: For patients with presumed PISPC, a biopsy followed by RT is recommended for skull base PISPC. However, the role of CMT is still not clear. Our findings need to be verified in a larger prospective cohort in the future. Systematic review registration number CRD42018098782.

Solitary Plasmacytoma of Bone of the Spine: Results From Surveillance, Epidemiology, and End Results (SEER) Registry.

STUDY DESIGN: Retrospective analysis. OBJECTIVE: To determine the prognostic indicators in patients with solitary plasmacytoma of bone (SPB) of the spine. SUMMARY OF BACKGROUND DATA: Population-level estimates for prognosis among patients with SPB of the spine are still lacking. Sociodemographic and clinical predictors of outcome have not been well characterized. METHODS: The Surveillance, Epidemiology, and End Results Registry was used to identify all patients with SPB of the spine from 1995 through 2014. Associated population data were used to determine annual incidence and limited-duration prevalence. Overall survival (OS) estimates were obtained using the Kaplan-Meier method and compared across groups using log-rank test. A Cox regression model was used for multivariate analysis of survival. Logistic regression was performed to identify predictors of the progression to multiple myeloma (MM). RESULTS: The incidence and prevalence of the disease increased during the study period. Spinal SPB most commonly affected older people (>50) with a male preponderance. The median OS were 74.0 months. The 5 and 10-year survival rates for these patients were 56.1% and 36.7%, respectively. On multivariable analyses, older age, and surgery without radiotherapy were correlated with poor survival of patients with spinal SPB. The 3-year probability of progression to MM was 10.1%. Patients aged >70 years were associated with progression to MM. There was no significant association between the methods of surgical resection (radical or local/partial) and OS or progression to MM. CONCLUSION: The findings of this study provide population-based estimates of the incidence, prevalence and prognosis for patients with SPB of the spine. This analysis indicated that the only identifiable prognostic indicators were older age and surgery without radiotherapy. Moreover, the methods of surgical resection did not influence the OS or progression to MM. LEVEL OF EVIDENCE: 4.

Perfil de pacientes com diagnóstico patológico de mieloma múltiplo em hospital de ensino / Profile of patients with multiple myeloma pathological diagnosis in a tea-ching hospital

Introdução: Plasmocitoma é um tumor maligno, originado da proliferação irreversível e autônoma dos plasmócitos, podendo se apresentar como massa circunscrita ou infiltração difusa. Quando há mais de um tumor de células plasmáticas, ocorre o chamado Mieloma Múltiplo. Essa neoplasia maligna de células B apresenta produção exagerada de uma das imunoglobulinas de cadeias leves Kappa ou Lambda. Objetivo: Avaliar possíveis associações entre dados epidemiológicos e a carga tumoral em pacientes com Mieloma Múltiplo. Material eMétodos: Trata-se de um estudo transversal, quantitativo, descritivo, realizado em prontuários de pacientes diagnosticados com Mieloma Múltiplo no Laboratório de Patologia do Hospital de Base do município de São José do Rio Preto, São Paulo, entre 2010 e 2014. Foram consideradas as variáveis: sexo, idade, presença de cadeia leve (Kappa, Lambda, ambas e não especificada), carga tumoral (leve, moderada e acentuada). Resultados:Analisamos 42 laudos de pacientes diagnosticados com Mieloma Múltiplo, sendo que 69% dos pacientes apresentaram idade igual ou superior a 60 anos, presença de imunoglobulina de cadeia leve Kappa em 59% e carga tumoral acentuada em 67% dos casos. Em relação ao sexo, observamos que o nível de carga tumoral acentuada ocorreu de maneira similar entre homens e mulheres. As mulheres diagnosticadas com carga tumoral leve ou moderada configuraram 71% dos pacientes, do estudo. Conclusão: A idade e sexo não constituem fator de risco para o Mieloma Múltiplo na amostragem avaliada, este fato pode estar relacionado ao tamanho amostral.

Introduction: Plasmocytoma is a malignant tumor, originated from the irreversible and autonomous proliferation of the plasmacytes, being able to present as circumscribed mass or diffuse infiltration. When there is more than one plasma cell tumor, the so-called Multiple Myelomas occurs. This malignant B cell neoplasm exhibits overproduction of one of the Kappa or Lambda light chain. Objective: To evaluate possible ssociation of epidemiological data with tumor burden in patients with multiple myelomas. Patients and Methods:It is a cross-sectional study conducted with medical records of patients diagnosed with multiple myeloma by the Pathology Laboratory in Hospital de Base in the city of São José do Rio Preto, São Paulo, between 2010 and 2014. We considered the variables gender, age, light chain presence (Kappa, Lambda, both and unspecified), and tumor burden (mild, moderate or severe). Results: We analyzed 42 medical records of patients diagnosed with multiple myelomas. Of these, 69% of patients were aged 60 and over. Immunoglobulin Kappa light chain was found in 59% patients, and severe tumor burden in 67% of them. Regarding sex, we observed that severe tumor burden level occurred in a similar manner in men and women, without significant associations. Women diagnosed with mild to moderate tumor burden corresponded to 71% of patients, but no significant association was found. Conclusion: Age and sex were not a risk factor for multiple myelomas in this evaluated sample. This may be due to the sample size evaluated.

Diagnosis, treatment, and response assessment in solitary plasmacytoma: updated recommendations from a European Expert Panel.

Solitary plasmacytoma is an infrequent form of plasma cell dyscrasia that presents as a single mass of monoclonal plasma cells, located either extramedullary or intraosseous. In some patients, a bone marrow aspiration can detect a low monoclonal plasma cell infiltration which indicates a high risk of early progression to an overt myeloma disease. Before treatment initiation, whole body positron emission tomography-computed tomography or magnetic resonance imaging should be performed to exclude the presence of additional malignant lesions. For decades, treatment has been based on high-dose radiation, but studies exploring the potential benefit of systemic therapies for high-risk patients are urgently needed. In this review, a panel of expert European hematologists updates the recommendations on the diagnosis and management of patients with solitary plasmacytoma.

Plasmocitoma solitario en pediatría: una rara entidad / Pediatric solitary bone plasmacytoma: a rare entity

El plasmocitoma en edad pediátrica es poco frecuente. Se presenta a una adolescente de 14 años que ingresó por una cuadriplejia fláccida asociada a una tumoración a nivel de cráneo y columna cervical. En el estudio histológico se diagnosticó un plasmocitoma en ambos sitios, sin infiltración medular. Recibió tratamiento con radio y quimioterapia. A los tres años se encontró una nueva lesión a nivel del ovario izquierdo, que coincidió histológicamente con el diagnóstico inicial. El plasmocitoma solitario de hueso se describe como el más común en edad pediátrica con tendencia a la recidiva tumora(AU)

Plasmacytoma in the pediatric age group is rare. We present a 14-year-old girl admitted with a flaccid quadriplegia associated with a tumor at the level of the skull and cervical spine. In the histological study plasmacytoma was diagnosed in both sites without bone marrow infiltration. The patient was treated with radiation and chemotherapy. After three years a new lesion on the left ovary was found, which histologically coincided with the initial diagnosis. Solitary bone plasmacytoma is described as the most common in pediatric patients prone to tumor recurrence(AU)

Incidence, characteristics, and outcome of solitary plasmacytoma and plasma cell leukemia. Population-based data from the Swedish Myeloma Register.

Solitary plasmacytoma (SP) and plasma cell leukemia (PCL) are uncommon (3-6%) types of plasma cell disease. The risk of progression to symptomatic multiple myeloma (MM) is probably important for the outcome of SP. PCL is rare and has a dismal outcome. In this study, we report on incidence and survival in PCL/SP, and progression to MM in SP, using the prospective observational Swedish Multiple Myeloma Register designed to document all newly diagnosed plasma cell diseases in Sweden since 2008. Both solitary bone plasmacytoma (SBP) (n=124) and extramedullary plasmacytoma (EMP) (n=67) have better overall survival (OS) than MM (n=3549). Progression to MM was higher in SBP than in EMP (35% and 7% at 2 years, respectively), but this did not translate into better survival in EMP. In spite of treatment developments, the OS of primary PCL is still dismal (median of 11 months, 0% at 5 years). Hence, there is a great need for diagnostic and treatment guidelines as well as prospective studies addressing the role for alternative treatment options, such as allogeneic stem cell transplantation and monoclonal antibodies in the treatment of PCL.

Solitary plasmacytoma: population-based analysis of survival trends and effect of various treatment modalities in the USA.

BACKGROUND: Solitary 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. METHODS: The 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. RESULTS: The 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). CONCLUSIONS: A 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.