A Plasmacytoma of the Lateral Pharyngeal Wall: A Diagnostic Enigma.

Plasmacytoma is a rare plasma cell dyscrasia that grows in bones or soft tissues such as the pharynx. Soft tissue plasmacytomas are rare, and a higher burden has been reported in the upper aero-digestive tract, often manifesting as hoarseness, dysphagia, or odynophagia. Due to their rarity, extramedullary plasmacytomas (EMPs) have unknown prognostic factors, and guidelines for optimal management are still lacking. However, radiation therapy and surgery have been used with positive outcomes. Herein, we describe a unique case of plasmacytoma of the pharyngeal tissue in a male patient with a history of HIV disease. The patient completed 28 sessions of radiation therapy, resulting in an improvement in his throat pain and hoarseness. Given the patient's age and lack of traditional risk factors for head and neck cancers, his hoarseness and odynophagia proved to be a diagnostic conundrum. Although infrequent, soft tissue plasmacytomas should be considered in the differential diagnosis of head and neck tumors.

Enhanced clinical outcomes with radiotherapy in diagnostically challenging intracranial plasmacytomas: Analysis of 190 cases.

BACKGROUND: Intracranial plasmacytomas are rare tumors arising from plasma cells with approximately half of the cases progressing to multiple myeloma (MM). However, there is a lack of comprehensive clinical cohort analysis on the clinical and pathological features, progression, and outcomes of intracranial plasmacytomas. METHODS: A retrospective analysis of 190 cases was conducted, combining data from 38 cases in a single institution and 152 cases from the literature. Patient demographics, clinical presentations, tumor locations, imaging features, surgical treatments, and follow-up outcomes were collected and analyzed. Survival analysis and Cox regression analysis were performed to identify prognostic factors. RESULTS: A total of 190 intracranial plasmacytoma patients with an average age of 55.4 years were included in the study. The preoperative misdiagnosis ratio was high at 55.3%, and 59.7% of the tumors affected the calvaria convexity, compared to 40.3% located at the skull base. Resection and biopsy were achieved in 72.4% and 27.6% patients, respectively. Among them, 34.2% (65/190) of patients were initially diagnosed with MM with intracranial plasmacytoma as their first presentation (MM-IPFP), while 63.2% (120/190) of patients were diagnosed with solitary intracranial plasmacytoma (SIP), including 61 extramedullary plasmacytomas and 59 solitary bone plasmacytomas. In the SIP group, 22.4% (24/107) of patients experienced disease progression leading to the development of MM during a median follow-up time of 42.6 months (range 1-230 months). Multivariate analysis unveiled that radiotherapy (HR, 0.05; 95% CI, 0.00-0.87; p = 0.04), not surgery, was a protective prognostic factor for overall survival in MM-IPFP patients. Comparison between the SIP progression group and non-progression group revealed a significant difference of Ki-67 index (non-progression vs. SIP progression, 8.82% ± 7.03 vs. 16.5% ± 10.5, p < 0.05). AUC analysis determined that a cutoff value of 9.0% was the best predictor of SIP progression, with an area under the curve of 0.712. CONCLUSIONS: This retrospective clinical analysis highlights the potential role of radiotherapy, rather than surgical resection, in improving the outcomes of intracranial plasmacytoma. Additionally, the Ki-67 index is identified as a valuable marker for predicting disease progression. This would provide some evidence for the paradigm of diagnosis and treatment modalities for intracranial plasmacytomas from the large cohort.

Extramedullary plasmacytoma of the larynx - Case report.

Extramedullary plasmacytoma of the larynx is an extremely rare entity accounting for 0.04-0.45% of malignant tumours of the larynx. The objective of this clinical case report is to highlight the diagnosis and management of a unique case such as this. A 77-year-old gentleman presented with complaints of hoarseness for 1 year. Computed tomography image revealed a soft tissue mass lesion involving the right true vocal cord. Direct laryngoscopic biopsy was performed and subjected to histopathological examination, which showed collection of plasma cells. Immunohistochemistry confirmed the presence of Kappa and Lambda cells. Multiple myeloma (MM) was ruled out. The patient received radical intent radiation therapy using 3DCRT technique with a dose of 50Gy in 25# over 5 weeks. He experienced improvement in hoarseness on subsequent follow-up visits. At 1-year follow up, positron emission tomography computed tomography showed near total resolution of disease with no progression to MM. Radiation therapy alone is known to achieve good local control, recurrence free survival, and organ preservation in such cases.

Case with translating to multiple myeloma at 8 years after radiation therapy for extramedullary plasmacytoma of the larynx.

We report a case of extramedullary plasmacytoma of the larynx that was eradicated by radiotherapy; however, 8 years later, the disease had progressed to multiple myeloma. A mid -60s Japanese woman presented with a right-sided arytenoid mass in the larynx who underwent biopsy at another hospital. Based on the biopsy results, the patient was diagnosed with extramedullary plasma cell tumour and was referred to the Department of Otorhinolaryngology at our hospital. She received radiotherapy (50.4 Gy) and the laryngeal tumour was eradicated. Positron emission tomography/CT (PET-CT) revealed no abnormal accumulation in the larynx or whole body. After radiotherapy, the department of otorhinolaryngology, in consultation with Ddepartment of haematology performed follow-ups using laryngoscope, blood examination and PET-CT. Five years after the end of radiotherapy, the patient had no local recurrence or transition to multiple myeloma. However, 8 years later, blood examination and PET-CT revealed multiple myeloma. Laryngoscopy did not reveal any recurrent laryngeal tumour. Therefore, chemotherapy for multiple myeloma was administered at the department of haematology. Three months after the initiation of chemotherapy, the accumulation had disappeared in PET-CT. Three years have passed since chemotherapy initiation. At present, no recurrence or metastasis was observed in the larynx or whole body.

[Recent Research Progress of Extramedullary Plasmacytoma --Review].

Extramedullary plasma cell tumor (EMP) is a kind of plasma cell tumor, and its pathogenesis is not completely clear. According to whether it is independent of myeloma disease, it can be divided into primary and secondary EMP, which have different biological and clinical characteristics. Primary EMP has low invasion, fewer cytogenetic and molecular genetic abnormalities and good prognosis, and surgery and / or radiotherapy are the mainly treatments. Secondary EMP, as the extramedullary invasive progression of multiple myeloma (MM), is often accompanied by high-risk cellular and molecular genetic abnormalities and poor prognosis, chemotherapy, immunotherapy and hematopoietic stem cell transplantation are the mainly treatment. This paper reviews the latest research progress of EMP in the pathogenesis, cytogenetics molecular genetics and treatment, so as to provide reference for clinical work.

Oral Extramedullary Plasmacytoma Treatment Using a Combination of Marginal Excision and Strontium-90 Therapy in Five Dogs.

Extramedullary plasmacytoma (EMP) is a benign round cell tumor that is most commonly found in cutaneous locations in dogs and occurs less frequently in the oral cavity. They are highly radiosensitive, are distinct from systemic multiple myeloma syndrome and wide surgical excision is typically curative. This report describes five cases of non-invasive oral EMP in dogs treated with a combination of marginal excision and strontium-90 plesiotherapy. All five cases had narrow or incomplete margins on histopathologic evaluation but experienced no recurrence after combination therapy. Plesiotherapy radiation may offer a potential adjunct treatment for non-invasive oral EMP by providing a superficial dose of radiation that complements a less invasive surgical removal. The combination of plesiotherapy and marginal excision may offer an alternative to wide surgical excision for non-invasive oral EMPs.

Radiographic Response of Solitary Plasmacytomas After Conformal Radiotherapy May Be Delayed: Outcomes in the 3D Era.

OBJECTIVE: Although recurrence rates after radiotherapy for solitary plasmacytoma (SP) are well established, little is known about how SP responds radiographically, as most historical patients were treated in the 2D era. We evaluated the response to radiotherapy among SP patients staged and treated with 3D techniques, including proton therapy, which has not yet been previously reported. METHODS AND MATERIALS: Between 2007 and 2021, 15 SP patients (4 extramedullary, 11 bone) staged with 3D imaging and bone marrow evaluation were consecutively treated with definitive radiotherapy. The best response was categorized in 9 evaluable patients according to response evaluation criteria in solid tumors (RECIST) and positron emission tomography response criteria in solid tumors (PERCIST). RESULTS: With a median follow-up of 34 months, 4 patients relapsed. The median time to the best response was ~2 years (26.6 mo RECIST, 25.4 mo PERCIST). Response rates differed based on response assessment criteria. PERCIST was associated with higher rates of complete (85.7%) or partial response (14.3%) compared with RECIST (16.7% complete, 33.3% partial). Two-year and 4-year PFS for extramedullary SP were 100% and 75%, compared with 91% and 55% for bone ( P =0.75). Patients treated with proton therapy (n=5) did not appear to have different patterns of relapse (1 marginal, 1 distant) compared with those treated with photons or electrons (n=10; 2 distant). CONCLUSIONS: More conformal dose distribution with proton therapy does not appear to alter patterns of recurrence. Although response rates differ based on criteria by both RECIST and PERCIST assessments, the radiographic response may be slow and requires validation in other cohorts.

A new prediction model for overall survival of elderly patients with solitary bone plasmacytoma: A population-based study.

Background: Comprehensive studies on the prognosis of solitary bone plasmacytoma (SPB) are lacking, especially in elderly patients with SPB. This study aims to establish a novel nomogram and risk stratification system to predict the overall survival (OS) of elderly patients with SPB. Methods: The data of elderly patients with SPB from 2000 to 2017 were identified in the SEER database. SPB patients were randomly assigned to the training set (n = 825) and validation set (n = 354). The Cox regression analysis was used to determine the independent risk factors for OS in elderly SPB patients. The nomogram was established and assessed by the area under the receiver operating curve (AUC), the consistency index (C-index), and the calibration plot. Patients were divided into low-, medium-, and high-risk groups based on the score of the nomogram. The Kaplan-Meier (K-M) curve was used to verify the differences in overall survival among the three groups. Result: A total of 1,179 elderly patients with SPB were included in the study. Age at diagnosis, prior cancer before SPB, marital status, radiotherapy, and chemotherapy were independent risk factors of OS. The AUC of the 3, 5, and 8-year OS in the training and validation sets were between 0.707 and 0.860. The C-index and calibration plot also indicated that the nomogram has great predictive accuracy and robustness. After risk stratification, patients in the high-risk group had the worst OS. Conclusion: A novel nomogram was built to predict the OS of elderly patients with SPB. It will help clinicians formulate more reasonable and personalized treatment strategies.

Plasmocitoma extramedular solitario rinosinusal: reporte de caso y revisión de literatura / Solitary extramedullary plasmacytoma of the rhinosinusal cavity: a case report and literature review

Resumen El plasmocitoma extramedular solitario (PES) es una neooplasia maligna infrecuente caracterizada por una proliferación aislada de células plasmáticas monoclonales en tejido extramedular. La localización más frecuente es en cabeza y cuello con predominio en el territorio rinosinusal, sin embargo, estas lesiones malignas representan menos del 1% de los tumores de esta región anatómica. El diagnostico requiere una alta sospecha clínica, análisis histopatológico acucioso, estudios serológicos y exámenes radiológicos sistémicos de acuerdo a los criterios diagnósticos establecidos en la literatura internacional. Se analiza el caso de un paciente masculino con un PES que se presentó como un tumor de fosa nasal derecha y obstrucción nasal de meses de evolución con hallazgos clínicos e imagenológicos inespecíficos. El diagnóstico definitivo se realizó mediante biopsia endoscópica nasal y estudio histopatológico. El tratamiento fue abordado de manera multidisciplinaria entre otorrinolaringología, hematología y radiooncología. De acuerdo a las guías internacionales, se decidió realizar radioterapia localizada con buen resultado clínico precoz. El PES requiere un abordaje multidisciplinario para lograr un diagnóstico y tratamiento oportuno, siendo imprescindible la exclusión del mieloma múltiple debido a las diferencias terapéuticas y en pronóstico clínico. El tratamiento puede realizarse con radioterapia y/o cirugía, siendo la radioterapia el pilar de tratamiento.

Abstract Solitary extramedullary plasmacytoma (SEP) is a rare malignant neoplasm characterized by isolated proliferation of monoclonal plasma cells in extramedullary tissue. The most frequent location is in the head and neck with a predominance in the rhinosinusal territory; however, these malignant lesions represent less than 1% of the tumors in this anatomical region. The diagnosis requires a high clinical suspicion, careful histopathological analysis, serological studies and systemic radiological examinations according to the diagnostic criteria established in the international literature. We analyze the case of a male patient with SEP that presented as a tumor of the right nostril and nasal obstruction of months of evolution with nonspecific clinical and imaging findings. The definitive diagnosis was made by nasal endoscopic biopsy and histopathological study. The treatment was approached by multidisciplinary teamwork. According to international guidelines, it was decided to perform localized radiotherapy with good early clinical results. SEP requires a multidisciplinary approach to achieve a timely diagnosis and treatment, being essential exclusion of multiple myeloma due to the therapeutic differences and prognosis. Treatment can be done with radiation therapy and/or surgery; radiation therapy is the mainstay of treatment.

Evaluation of extramedullary plasmacytoma of the larynx with radiologic and histopathological findings.

Extramedullary plasmacytoma (EMP) is a plasma cell neoplasm of soft tissue without bone marrow involvement or other systemic characteristics of multiple myeloma. Approximately 80%-90% of EMPs involve the head and neck region, especially in the nasal cavity, paranasal sinuses, tonsillar fossa, and oral cavity. An EMP of the larynx is extremely rare and is a locally destructive lesion without systemic spread. Clinical features vary depending on the tumor location. A diagnosis is established by histopathology, immunohistochemistry, and a systemic survey to exclude systemic plasma cell proliferative diseases. Extramedullary plasmacytomas are highly radiosensitive and radiotherapy is therefore used as a treatment. In this study, we report on a rare case of EMP of the larynx evaluated with computed tomography and present histopathologic findings for a 74-year-old female patient.

Evaluación del plasmocitoma extramedular de laringe con hallazgos radiológicos e histopatológicos / Evaluation of Extramedullary Plasmacytoma of the Larynx with Radiologic and Histopathological Findings

El plasmocitoma extramedular (PEM) es una neoplasia de células plasmáticas del tejido blando sin afectación de la médula ósea ni otras características sistémicas de mieloma múltiple. Aproximadamente el 80-90% de los PEM afectan a la región de la cabeza y el cuello, especialmente a la cavidad nasal, los senos paranasales, la fosa amigdalina y la cavidad oral. Los casos de PEM de laringe son extremadamente raros y se trata de una lesión destructiva a nivel local sin propagación sistémica. Las características clínicas varían en función de la localización del tumor. El diagnóstico se establece mediante histopatología, inmunohistoquímica y un estudio sistémico para excluir las enfermedades sistémicas de proliferación de células plasmáticas. Los plasmocitomas extramedulares son altamente sensibles a la radiación, por lo que se utiliza la radioterapia como tratamiento. En este estudio, notificamos un caso raro de PEM de laringe evaluado con tomografía computarizada y presentamos los resultados histopatológicos de una paciente de 74 años.(AU)

Extramedullary plasmacytoma (EMP) is a plasma cell neoplasm of soft tissue without bone marrow involvement or other systemic characteristics of multiple myeloma. Approximately 80-90% of EMPs involve the head and neck region, especially in the nasal cavity, paranasal sinuses, tonsillar fossa, and oral cavity. An EMP of the larynx is extremely rare and is a locally destructive lesion without systemic spread. Clinical features vary depending on the tumor location. A diagnosis is established by histopathology, immunohistochemistry, and a systemic survey to exclude systemic plasma cell proliferative diseases. Extramedullary plasmacytomas are highly radiosensitive and radiotherapy is therefore used as a treatment. In this study, we report on a rare case of EMP of the larynx evaluated with computed tomography and present histopathologic findings for a 74-year-old female patient.(AU)

[Benefits of radiotherapy for patients with solitary plasmacytoma or multiple myeloma]. / Nutzen der Radioonkologie beim solitären Plasmozytom oder multiplen Myelom.

BACKGROUND: Treatment options for patients with solitary plasmacytoma (SP) or multiple myeloma (MM) should be discussed in an interdisciplinary context. This systematic review focuses on the importance of radiotherapy in MM and SP. OBJECTIVE: Summary of local radio-oncological treatment options for patients with SP and MM. MATERIALS AND METHODS: Based on a systematic literature search, the current evidence on the topic was analyzed and summarized. RESULTS: Patients with SP should be primarily treated with radiotherapy with or without surgery. Irradiation concepts may vary depending on risk factors and manifestation (solitary bone plasmacytoma vs. solitary extramedullary plasmacytoma). Although local control rates are high after radiotherapy, progression to multiple myeloma frequently occurs. In patients with MM, radiation is mainly used in palliative settings for pain relief, prevention of fractures or in patients who suffer from neurological symptoms due to spinal cord compression. Irradiation dose and fractionation should be selected based on treatment indication and general condition of the patient. CONCLUSION: Although most patients receive systemic treatment at initial diagnosis, approximately 40% of patients with MM will require radiation during the course of their disease. While radiation is mainly used for palliation in patients with MM, it represents the primary and curative treatment option in patients with SP.

Case report: gastric plasmacytoma resistant to radiation therapy.

Plasma cell neoplasms are a group of diseases involving the malignant proliferation of plasma cells. One common type of plasma cell neoplasm is multiple myeloma, which typically occurs diffusely in the bone marrow. It can manifest with a variety of presentations, including bone pain, fractures, anemia, infection, hypercalcemia, and renal failure. A less common type of plasma cell neoplasm is the solitary plasmacytoma, which is a local proliferation of plasma cells in the bone or extramedullary tissues. They rarely recur after local radiation therapy.An 83-year-old woman was noted on routine labwork to have elevated total serum protein, and serum immunofixation confirmed IgG/Kappa paraprotein. There was no evidence of end-organ damage characteristic of myeloma: hypercalcemia, renal dysfunction, anemia, or bone lesions. She was diagnosed with monoclonal gammopathy of undetermined significance and placed on observation. Seven years later, she developed mild anemia and an increasing M spike. No abnormalities were found on bone marrow biopsy apart from mildly increased plasma cell proliferation (7-10% of total cells). A PET scan showed increased gastric uptake, concerning for possible gastric malignancy. Upper gastrointestinal endoscopic ultrasound revealed extrinsic compression of the stomach fundus and body due to a 40 mm mass and associated adenopathy. Pathology revealed a kappa-restricted plasma cell neoplasm positive for CD138.The patient underwent radiation therapy localized to the gastric area. Subsequent evaluation revealed a persistent gastric mass. Attempted biopsy resulted in a gastrointestinal bleed, rendering her unable to undergo treatment with lenalidomide and aspirin. She is currently undergoing chemotherapy with bortezomib, cyclophosphamide, and dexamethasone. The case illustrates the potential diversity of plasma cell dyscrasia clinical manifestations. Gastric plasmacytomas are an uncommon type of extramedullary plasmacytoma, particularly rare when resistant to radiation therapy.

[Role of radiotherapy in haematology]. / Place de la radiothérapie en hématologie.

The management of myeloid and lymphoid disease is essentially based on chemotherapy and targeted therapies. Since radiotherapy could be responsible for severe late toxicities, essentially due to conventional bidimensional irradiation techniques, many trials have attempted to omit radiotherapy or to scale down the dose in their therapeutic strategy. Nevertheless, radiotherapy still plays a role for curative or symptomatic purposes.

Safety and Feasibility Analysis of a Prospective Trial on Stereotactic Body Radiotherapy for Solitary Bone Plasmacytoma.

BACKGROUND: There have been reports on the use of hypofractionated stereotactic body radiotherapy (SBRT) for bone plasmacytomas, but no prospective data are available. We present the initial analysis of an ongoing prospective protocol on SBRT addressing the feasibility and safety of this treatment for solitary bone plasmacytomas. PATIENTS AND METHODS: A prospective cohort of SBRT for solitary bone plasmacytoma was developed. Patients could receive different doses depending on the index bone, from single fraction for skull base lesions, 24 Gy in 3 fractions for spine lesions, and 30 Gy in 5 fractions for other bones. Overall survival, bone events, local control, and progression to multiple myeloma (MM) were measured and compared to our retrospective cohort of patients treated with conformal standard-dose radiotherapy. Quality of life was assessed via the EORTC QLQ-C30 questionnaire, and toxicities were assessed by the CTCAE v5.0 criteria. After 1 year or the inclusion of 5-10 patients, a feasibility and safety analysis was programmed. RESULTS: Between April 2018 and April 2019, 5 patients were included. All were male, with a median age of 53.1 years. The median follow-up was 21.8 months. No patient had local progression, bone event, or died. Two patients had progressions to MM. The mean survival free of progression to MM was 18.6 months, compared to 19 months in the retrospective cohort; median values were not reached. There were no grade 3 toxicities. CONCLUSION: SBRT for plasmacytoma is safe and feasible. More robust data are awaited.

Rare case of anaplastic plasmacytoma in the sinonasal tract.

BACKGROUND: Extramedullary plasmacytomas are tumors that develop from plasma cells and rarely express anaplastic features. To our knowledge, there have only been three reported cases of anaplastic plasmacytomas of the sinonasal tract in the English literature. We detail the fourth case. METHODS: A 70-year-old male was seen with a 4-month history of nasal congestion, bloody mucous, and left sided nasal obstruction. On positron emission tomography/computed tomography, the lesion was FDG-avid with an SUVmax of 25.1. A biopsy of the lesion and subsequent immunohistochemical staining confirmed the diagnosis of an anaplastic plasmacytoma. RESULTS: The patient is undergoing a 5-week course of curative-intent radiation therapy. CONCLUSION: Extramedullary plasmacytomas with anaplastic features are very rare. We highlight the value of thorough histopathological review and detailed immunostains to arrive at a diagnosis of anaplastic extramedullary plasmacytoma.

Solitary extramedullary plasmacytoma of the nasopharynx: The role of flow cytometry.

Extramedullary plasmacytoma (EMP) represents a distinct yet rare entity among the plasma cell neoplasms. Given its rarity, no therapeutic consensus has been met. We report the case of a 57-year-old man with a one-year history of nasal congestion and occasional dyspnoea. Imaging showed a hypermetabolic mass in the right nasopharynx extending backward towards the adjacent oropharynx, infiltrating the epiglottis. As incisional biopsy showed histologic and immunophenotypic features consistent with plasma cell neoplasm, whereas the possibility of a marginal zone lymphoma with plasmacytic differentiation was included in the differential diagnosis. A final diagnosis of EMP was reached by using flow cytometry (FC) of a cell suspension from the neoplastic tissue. The patient received local radiotherapy (RT) which resulted to complete remission. In conclusion, flow cytometry might serve as an auxiliary method in cases where immunohistochemistry cannot differentiate between a plasma cell dyscrasia and a B-non-Hodgkin lymphoma. In cases of an established diagnosis of solitary nasopharyngeal EMP RT represents an excellent treatment modality offering prolonged disease-free survival.

Intraocular solitary extramedullary plasmacytoma presenting as unilateral anterior and intermediate uveitis preceded by refractory glaucoma.

BACKGROUND: Solitary extramedullary plasmacytoma (SEP) is a localised proliferation of monoclonal plasma cells involving soft tissue with no or minimal bone marrow involvement and no other systemic evidence of multiple myeloma. Intraocular involvement is exceedingly rare. CASE PRESENTATION: We report a 78-year-old man who was referred with glaucoma in the right eye. He subsequently developed anterior chamber (AC) inflammation and refractory glaucoma then dense vitritis. A vitrectomy was performed with the biopsy revealing numerous plasma cells with atypical findings. In conjunction with the flow cytometry results, and a systemic work up excluding multiple myeloma, a diagnosis of SEP was made. The patient was treated with ocular external beam radiotherapy with resolution of the intraocular inflammation and control of the intraocular pressure. He remains well with no local recurrence and no development of multiple myeloma over a follow up period of 2.5 years. CONCLUSIONS: This is the first case report of SEP presenting as intraocular inflammation without a uveal tract mass.

Radiotherapy for the treatment of solitary plasmacytoma: 7-year outcomes by a mono-institutional experience.

OBJECTIVES: Solitary plasmacytoma (SP) is characterized by a single mass of clonal plasma cells. Definitive RT can result in long-term local control of the SP. Due to the small number of patients and narrow range of doses, phase III randomized trials are lacking. The aim of this study is to further support the potential use of RT for the treatment of SP. METHODS: Clinical data of all patients treated for SP at our Institution between 1992 and 2018 were reviewed. A total of 42 consecutive patients were analyzed. RESULTS: The median follow-up was 84.8 months. Radiation dose did not differ significantly as a function of sex, type of SP (solitary bone plasmacytoma or as extramedullary plasmacytoma), tumor size; conversely differs significantly as a function of age (p = 0.04). The 5y-OS and 10y-OS were, respectively, 96 and 91%. Local recurrences developed in 21.4% of patients (9/42). 16 patients progressed to MM (38.1%). The 5y-progression to MM free survival (PMFS) and the 10y-PMFS were, respectively, 68.6 and 61.9%. CONCLUSIONS: Our data confirm that good results are achievable with RT to treat SP, but they don't allow defining a dose-effect correlation; therefore, it remains uncertain which is the most effective dose and whether lower doses can guarantee adequate disease control.