These initial studies should be compared with subsequent values at a later time, when it is necessary to decide whether the disease is stable or progressive, responding to treatment, or getting worse.
As mentioned before, the major challenge is to separate the stable, asymptomatic group of patients who do not require treatment from patients with progressive, symptomatic myeloma who should be treated immediately.[6,7]
Monoclonal Gammopathy of Undetermined Significance (MGUS)
Patients with MGUS have an M protein in the serum without findings of multiple myeloma, macroglobulinemia, amyloidosis, or lymphoma and have fewer than 10% of plasma cells in the bone marrow.[2,16,17] Patients with smoldering myeloma have similar characteristics but may have more than 10% of marrow plasma cells.
These types of patients are asymptomatic and should not be treated. They must, however, be followed carefully since about 1% to 2% of MGUS patients per year will progress to develop myeloma (most commonly), amyloidosis, lymphoma, or chronic lymphocytic leukemia and may then require therapy.[18,19]
Virtually all cases of multiple myeloma are preceded by a gradually rising level of MGUS.[20,21,22]
Risk factors that predict disease progression include the following:
- An abnormal serum-free light chain ratio.
- Non-IgG class MGUS.
- A high serum M protein level (?15 g/L).
Isolated Plasmacytoma of Bone
The patient has an isolated plasmacytoma of the bone if the following are found:
- A solitary lytic lesion of plasma cells is found on skeletal survey in an otherwise asymptomatic patient.
- A bone marrow examination from an uninvolved site contains less than 10% plasma cells.[24,25,26]
When clinically indicated, MRI may reveal unsuspected bony lesions that were undetected on standard radiographs. MRI scans of the total spine may identify other bony lesions.
A patient has extramedullary plasmacytoma if the following are found:
- Isolated plasma cell tumors of soft tissues, most commonly occurring in the tonsils, nasopharynx, or paranasal sinuses.
- Negative findings on skeletal x-rays and bone marrow biopsy.[28,29,30]
Multiple myeloma is a systemic malignancy of plasma cells that typically involves multiple sites within the bone marrow and secretes all or part of a monoclonal antibody.
Multiple myeloma is highly treatable but rarely curable. The median survival in the prechemotherapy era was about 7 months. After the introduction of chemotherapy, prognosis improved significantly with a median survival of 24 to 30 months and a 10-year survival of 3%. Even further improvements in prognosis have occurred because of the introduction of newer therapies such as pulse corticosteroids, thalidomide, bortezomib, and autologous and allogeneic stem cell transplantation, with median survivals of 45 to 60 months.[31,32,33]
Multiple myeloma is potentially curable when it presents as a solitary plasmacytoma of bone or as an extramedullary plasmacytoma. (Refer to the Isolated Plasmacytoma of Bone and Extramedullary Plasmacytoma sections of this summary for more information.)