A study published in the Journal of Clinical Oncology reports that risk of osteonecrosis of the jaw (ONJ) in patients with multiple myeloma may increase with age, time since diagnosis of multiple myeloma, long-term use of bisphosphonates, and recent dental extractions.
Multiple myeloma is a cancer of plasma cells. Plasma cells are a special type of white blood cell that are part of the body’s immune system. Plasma cells normally live in the bone marrow and make proteins, called antibodies, that circulate in the blood and help fight certain types of infections. Plasma cells also play a role in the maintenance of bone by secretion of a hormone, called osteoclast activating factor, which causes the breakdown of bone.
In multiple myeloma, plasma cells infiltrate the bone marrow, spreading into the cavities of all the large bones of the body. As the number of plasma cells increases and greater amounts of proteins are produced, patients experience decreased bone marrow blood cell production, fragility of the bones, pain, and abnormal kidney function. They may also have decreased quantities of normal antibodies necessary to fight certain types of infection.
Bisphosphonates are a class of drugs used to treat multiple myeloma, cancer-related hypercalcemia (high levels of calcium in the blood), and bone metastases in patients with advanced cancers. Zometa® (zoledronic acid) and Aredia® (pamidronate) are two potent bisphosphonates that are approved for use in specific subsets of cancer patients.
There have been reports of ONJ among patients treated with Zometa and Aredia, but the frequency of ONJ and risk factors for ONJ have not been well defined. To describe the features of ONJ among patients with multiple myeloma, researchers compared the characteristics of 22 patients with ONJ and 68 patients without ONJ. They noted the following:
- Median time from diagnosis of multiple myeloma to development of ONJ was 4 years.
- Pain was the most common symptom at diagnosis of ONJ.
- Compared to patients without ONJ, patients with ONJ were more likely to report recent dental extractions or treatment with Aredia followed by Zometa. Patients with ONJ were also older and had been living with multiple myeloma for a longer time.
The researchers conclude that ONJ is an emerging problem among patients with multiple myeloma. Although long-term bisphosphonate use was one of the factors that appeared to increase the risk of ONJ, the researchers note that bisphosphonates provide important benefits for many patients.
Patients who plan to use bisphosphonates for longer than two years may wish to discuss the risks and benefits with their physician.
Reference: Badros A, Weikel D, Salama A et al. Osteonecrosis of the Jaw in Multiple Myeloma Patients: Clinical Features and Risk Factors. Journal of Clinical Oncology. 2006;24:945-952.