What is Myeloma Bone Disease?
Myeloma means, literally, a "tumor composed of cells normally found in bone marrow." The majority of patients with myeloma develop destructive bone lesions, also known as osteolytic bone lesions. These lesions occur primarily in the vertebrae, the ribs, the pelvis, and the skull. They occur in the red bone marrow where nests of myeloma cells accumulate. Myeloma cells do not have a direct effect on the skeleton; rather, they cause bone destruction by producing signals that activate normal osteoclasts to resorb bone. Why this occurs is not clearly understood. There is currently, however, a large amount of research directed at understanding the mechanisms by which bone is destroyed by myeloma cells.
The skeletal lesions that occur in myeloma not only result in pain, pathological fractures, and hypercalcemia, but sometimes deformity and occasionally nerve compression syndromes. The lesions occur most commonly in the vertebrae. The appearance of the vertebral spine may resemble osteoporosis radiologically although the histologic abnormalities are quite different.
How often does it occur?
The incidence of myeloma is 3-4/100,000 in the U.S., which translates into approximately13,500 new cases of myeloma in the U.S. each year. Myeloma is more common in blacks than whites, and the male/female ratio is 3:2. The incidence varies from country to country, with a higher incidence found in most Western industrialized countries. Over the past 30 years there has been a 400% increase in the incidence of the disease. This apparent increase is probably due to better diagnostic techniques and the higher average age of the general population. However, more frequent myeloma in patients under age 55 may indicate environmental causative factors over the past three decades.
Symptoms
Approximately 70% of myeloma patients experience pain of varying intensity, often in the lower back. Sudden severe pain can be a sign of fracture or collapse of a vertebra. Patients also have general malaise and vague complaints. Hypercalcemia (too much calcium in the blood), which is present in 30% of patients, can cause tiredness, thirst, and nausea, and usually occurs when a patient has impaired kidney function.
Treatment
It is not yet possible to cure myeloma, although it is possible to improve the clinical status and the survival in patients through the use of chemotherapy, alpha interferon and, possibly, bone marrow transplants.
For myeloma patients with hypercalcemia, the goal is to treat the hypercalcemia and its potentially dangerous complications. In these patients, hypercalcemia is always associated within creased bone resorption and frequently with impaired kidney function. The best approach is to treat the myeloma itself and to treat the hypercalcemia with drugs that inhibit bone resorption, such as bisphosphonates, and the careful use of intravenous fluids. Bisphosphonates have been very effective in the treatment of hypercalcemia of myeloma.
The more common situation is the patient with myeloma bone disease who does not havehypercalcemia. Until recently, these patients have been treated for the bone disease with symptomatic therapy, namely: analgesics for pain, orthopedic treatment for fractures, or local radiation therapy for localized bone pain. Recent studies have indicated that potent bisphosphonates, such as pamidronate and clodronate, may have beneficial effects in patients with myeloma. In some patients, pain is reduced, the need for analgesics is less, episodes of fracture and hypercalcemia are reduced, and the need for radiation therapy for bone pain is lessened. As a consequence, pamidronate has received FDA approval in the U.S. for treatment of not just hypercalcemia in myeloma, but also myeloma bone disease in the absence of hypercalcemia. Further studies are ongoing to determine the effects of bisphosphonates on survival of patients, the ideal dose and duration, and whether other new and more potent bisphosphonates have similar beneficial effects. One important and unanswered question is whether bisphosphonates should be used in patients who do not as yet have symptoms or evidence of bone disease.
Other points are important in the management of patients with myeloma bone disease. These include the management of severe bone pain and the avoidance of fractures. Patients with severe pain that is localized often do well with a course of local radiation therapy, particularly when the bone disease is localized in the vertebral spine. Analgesic use is warranted as needed for severe bone pain. Patients will do best when they have an understanding of their bone disease and what activities put them at risk for further complications. The same principles that apply to patients with osteoporosis also apply to those with myeloma bone disease. Patients should avoid those lifestyle situations that are potentially dangerous (e.g., climbing ladders or slipping on ice or loose bathroom rugs).
