Approach Considerations
Due to the rarity of solitary plasmacytoma (SP), there are no randomized studies to inform the best treatment approach, and the available data from small case series are controversial. Radiotherapy is the treatment of choice for SP, although its efficacy has been tested only in small retrospective series. [45]
Experts have yet to reach a consensus regarding the optimal treatment modality for extramedullary plasmacytoma (EMP). Current guidelines stipulate that head and neck EMP be treated with radiotherapy only, as surgical resection of these tumors can be highly invasive. [47]
Chemotherapy, with regimens used in multiple myeloma, may be considered. Mignot et al reported that combining lenalidomide plus dexamethasone with radiation therapy improved myeloma-free survival and progression-free survival, compared with radiation therapy alone, in patients with SP. [48]
In a retrospective study by Thumallapally et al, 825 patients (49%) received radiotherapy and 197 (12%) underwent surgery, while 359 patients (21%) required both radiotherapy and surgery. The majority of SBP patients received radiation, while patients with EMP of upper airway tract and the central nervous system most commonly received radiotherapy plus surgery; those with lower airway tract involvement received radiotherapy only or neither radiotherapy nor surgery, and those with gastrointestinal tract localization were more frequently treated with surgery only. [2]
The survival rates of patients treated with radiotherapy were significantly higher than those of patients who did not receive radiotherapy (64.4% vs. 48.6%, P < 0.05). Moreover, patients who received neoadjuvant radiotherapy had a greater chance of 5-year relative survival than those who received adjuvant radiotherapy (86% vs. 73%, P < 0.05). A significant difference in survival was also observed in patients who underwent surgery, compared with patients who did not (69.7% vs 57.4%, P < 0.05). [2]
Medical Care
Solitary bone plasmacytoma
Local radiotherapy is the treatment of choice for solitary bone plasmacytome (SBP). [10, 7, 14, 20, 41] Treatment fields should be designed to encompass all disease observed on MRI and should include a margin of healthy tissue (at least 2 cm). For spinal lesions, the margins should include at least 1 uninvolved vertebra.
Local control is achieved in 88-100% of patients. Virtually all patients have major symptom relief, [14] and the local tumor recurrence rate is approximately 10%.
Most centers use approximately 40 Gy for spinal lesions and 45 Gy for other bone lesions. For lesions larger than 5 cm, 50 Gy should be considered.
No dose-response relationship between radiation dose and disappearance of monoclonal protein was noted in a series of patients with SBP, as reported by Liebross et al. [20] Monoclonal protein is markedly reduced after radiotherapy in the majority of patients, but protein disappearance is observed in only 20-50% of patients. [15] Persistence of a serum monoclonal protein after initial radiation therapy predicts a higher risk of progression to multiple myeloma, so monitoring of serum electrophoresis and immunofixation after the completion of therapy is mandatory in such patients. [41]
Surgery is contraindicated in the absence of structural instability or neurologic compromise. [47]
Chemotherapy may be considered for patients not responding to radiation therapy. Regimens useful in multiple myeloma can be considered. [47] Mignot et al reported improved results with the addition of lenalidomide-dexamethasone to intensity-modulated radiation therapy (IMRT). [48, 49] No role exists for adjuvant chemotherapy in SBP.
Extramedullary plasmacytoma
Based on the documented radiation sensitivity of plasma cell tumors, the accepted treatment of extramedullary plasmacytoma (EMP) is radiotherapy.
When a lesion can be completely resected, surgery provides the same results as radiotherapy.
Combined therapy (surgery and radiotherapy) is an accepted treatment depending on the resectability of the lesion. [10, 13, 14, 15, 16] In fact, combination treatment may provide the best results. [15]
The optimal radiation dose for local control is 40-50 Gy (depending on tumor size) delivered over 4-6 weeks. [14, 15, 16]
Because of the high rate of lymph node involvement, local nodes should be included in the radiation field. [14]
Adjuvant radiotherapy should be recommended to patients with positive surgical margins.
Chemotherapy may be considered for patients with refractory or relapsed disease. Regimens used for multiple myeloma can be considered. [47]
Adjuvant chemotherapy may be considered for patients with tumors larger than 5 cm, as well as those with high-grade histology.
Surgical Care
Surgery is considered a specific treatment for plasmacytomas for distinct localizations (eg, spine with neurological damage, upper airway that cannot be treated with radiotherapy, or vertebral fractures that require stabilization). [45, 2]
Radical surgery of EMP of the neck and head with curative intent is often a mutilating procedure; because these tumors are highly radiosensitive, radical surgery should be avoided. However, for other sites, surgical removal, if feasible, should be considered. It is unclear whether additional treatment with radiotherapy is necessary for resected EMP with clear surgical margins. [45]
Consultations
Orthopedic evaluation is recommended for patients with solitary bone plasmacytoma (SBP) because lesions may cause spinal cord compression syndrome or pathologic fractures. Therapeutic procedures, such as kyphoplasty, can be implemented in order to restore vertebral structure.
An ear, nose, and throat evaluation is recommended for patients with extramedullary plasmacytoma (EMP) of the head and neck to precisely localize the lesion, obtain an adequate biopsy (including lymph nodes), and plan possible resection.
Long-Term Monitoring
Periodic evaluation for progression and development of multiple myeloma is recommended every 6 weeks for the first 6 months for solitary bone plasmacytoma (SBP) and extramedullary plasmacytoma (EMP), with extension of clinic appointments thereafter. Besides a complete history and physical examination, the following tests are recommended:
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Complete blood cell (CBC) count
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Complete metabolic panel with lactic dehydrogenase (LDH), calcium, phosphorus, C-reactive protein (CRP), and beta2 microglobulin
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Erythrocyte sedimentation rate (ESR)
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Serum protein electrophoresis with immunofixation
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Serum immunoglobulin quantification
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Urinary protein electrophoresis with immunofixation (24-h urine sample)
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Skeletal bone survey
Orthopedic follow-up is recommended for solitary bone plasmacytoma (SBP) and/or ear-nose-throat follow-up is recommended extramedullary plasmacytoma (EMP), based on the tumor location.
