Reader Question: What is Bisphosphonate-Associated Osteonecrosis of the Jaw (ONJ)? How common is ONJ, and what are its risk factors?
Not a day goes by when these questions do not come up. It appears that a significant amount of lawyers’ advertisements as well as newspaper and magazine articles have raised public opinion and thought on the matter. Recent news coverage focuses on new lawsuits against Merck, the maker of Fosamax (alendronate sodium), for causing deterioration of the mouth and exposure of the jaw bone. Here is a summary of the information I have been telling my patients as well as what has been released by the American College of Rheumatology.
Intravenous BisphosphonateThere are 368 cases of bisphosphonate-associated ONJ published between 1966 and January 31, 2006. Sixty percent of cases occurred after oral surgery for dental extraction or other dentoalveolar surgery, whereas the remainder occurred spontaneously, some in patients wearing dentures. Most cases (94%) occurred in patients treated with intravenous bisphosphonates (zoledronic acid (Zometa), pamidronate (Aredia)), and most (85%) had multiple myeloma or breast cancer metastatic to the skeleton. Patients receiving intravenous bisphosphonates for cancer were most often treated with one or more of the potent nitrogen-containing intravenous bisphosphonates, i.e., zoledronic acid or pamidronate, typically once a month for several years. The highest risk of ONJ appears to be associated with frequent, typically monthly, infusions of intravenous zoledronic acid, which has been widely used in patients with myeloma, breast cancer, and prostate cancer in recent years. ONJ typically appears as a lesion in the mouth with areas of exposed yellow-white hard bone with smooth or ragged borders.The main risk factors identified to date include cancer, frequent infusions of intravenous nitrogen-containing bisphosphonates, and dentoalveolar trauma (4-6). Risk factors have not been identified in patients receiving oral bisphosphonates, such as Fosamax, for postmenopausal osteoporosis without cancer.
Oral Bisphosphonate (Fosamax, Actonel, Boniva)
What about ONJ in patients without cancer? The total number of cases of non-cancer patients with ONJ associated with oral bisphosphonate therapy reported among several million estimated patients who have been exposed to these drugs over the last 20 years appears small. To date, fewer than 20 cases of ONJ have been reported in the medical literature among patients without cancer treated with oral bisphosphonates (Fosamax, Actonel, and Boniva).
Most of these cases are associated with alendronate (Fosamax) therapy, likely due to its wider use than other oral bisphosphonates. Thirteen of the Alendronate-treated cases occurred in patients treated for osteoporosis without cancer. One case of ONJ was associated with oral risedronate (Actonel), and one case with oral ibandronate (Boniva), both in patients treated for osteoporosis without cancer.