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The evaluation of an individual thought to have multiple myeloma may reveal a solitary plasmacytoma. A solitary plasmacytoma is a single cancer site that may involve the bone (osseous) or other tissues (extraosseous or extramedullary). Solitary plasmacytomas represent approximately 5% of all patients with myeloma.

Diagnosis of a solitary plasmacytoma requires a very thorough evaluation to ensure that there is not the presence of myeloma elsewhere in the body. This is because many patients who are presumed to have solitary plasmacytoma, are ultimately found to have evidence of myeloma elsewhere. Following complete evaluation, patients with solitary plasmacytoma can be treated with radiation therapy alone, as studies have indicated that the addition of chemotherapy to radiation does not improve overall survival in patients with solitary plasmacytoma.

Initial treatment options for patients with solitary plasmacytoma include radiation alone or the combination of chemotherapy and radiation. 

Radiation therapy for solitary plasmacytoma typically delivers between 40 and 50 Gy. Treatment with radiation is associated with up to 50% of patients with solitary bone plasmacytoma being alive without evidence of recurrence 10 years from treatment, suggesting that many patients with solitary plasmacytoma can be cured. Prognosis may be even better for patients with solitary extramedullary plasmacytoma. Both osseous and extraosseous or extramedullary plasmacytomas are treated with radiation therapy.1

Research suggests that treatment with chemotherapy for patients with solitary plasmacytoma may be delayed until the detectable progression of cancer and/or further symptoms of the cancer are exhibited in the patient.

Multiple myeloma is a cancer involving important immune (infection fighting) cells called plasma cells. Plasma cells aid the body in fighting infection by producing specialized proteins, called antibodies, which have the ability to target and/or kill foreign cells. In multiple myeloma, cancerous plasma cells produce abnormal and excessive antibodies that do not have the ability to properly fight infection. In addition, the cancerous plasma cells accumulate in the bone marrow suppressing the normal formation and function of other cells that are necessary for normal production of blood cells and immune functions. Ultimately, the excessive accumulation of cancer cells in the bone marrow leads to the formation of tumors in the bone, called plasmocytomas, causing the bone to break down. Solitary plasmacytoma is the existence of a solitary cancerous tumor in the bone with no detectable myeloma cells elsewhere in the body.

Diagnosis of multiple myeloma includes the detection of proteins produced by the cancer cells, called M-proteins, which can be found in the blood or urine of persons with this cancer. Following diagnosis and/or treatment of multiple myeloma, measurements of M-protein levels, in addition to other medical tests, may be used to continually monitor the status of the cancer and how it responds to certain treatments. There has been controversy regarding the use of chemotherapy for initial treatment in patients with solitary plasmacytoma versus delaying chemotherapy treatment until the cancer progresses. 

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There are two main reasons to delay chemotherapy treatment: 1) early exposure to a chemotherapy drug potentially creates cancer cells that are resistant to the effects of that drug, restricting treatment options later in the disease when it may be more useful; 2) exposure to chemotherapy can induce the development of second cancers later in a patient’s life.

Researchers at the MD Anderson Cancer Center recently evaluated the outcomes of over 125 patients with solitary plasmacytomas receiving only radiation therapy as initial treatment. Radiation controlled the local plasmacytoma in over 90% of the patients. Cancer recurrences occurred in only 20% of patients who showed a disappearance of M-protein following treatment with radiation. Patients who did not show a decrease in M-protein levels following radiation therapy had a 60% chance of recurrence. This data was compared to other studies evaluating the outcome of patients with solitary plastmacytoma who received both chemotherapy and radiation as initial treatment. The addition of chemotherapy to radiation therapy showed no overall benefit regarding the rate of cancer progression. However, the treatment of chemotherapy did show a delay to cancer progression in a minority of patients.

The results from this study indicate that the addition of chemotherapy to radiation therapy showed no benefit in decreasing the overall chance of cancer progression for patients with solitary plasmacytoma. The role of initial chemotherapy treatment has not yet been definitively determined and further clinical trials are needed to distinguish which patients may benefit from more aggressive initial treatment including chemotherapy and which patients should be spared from unneeded treatment and it’s associated side effects. Persons with solitary plasmacytoma may wish to speak with their physician about the risks and benefits of initial treatment including chemotherapy or about the participation in a clinical trial further evaluating chemotherapy or other promising new treatment strategies. 

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  1. Rajkumar SV, Dispenzieri A, Kyle RA. Monoclonal gammopathy of undetermined significance, Waldenström macroglobulinemia, AL amyloidosis, and related plasma cell disorders: diagnosis and treatment. Mayo Clinic Proceedings. 2006;81:693-703.Blood
  2. Blood. Vol 96, No 6, pp 2037-2044, 2000.

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