Nitrogen-containing and non–nitrogen-containing bisphosphonates have been implicated in the development of osteonecrosis of the jaw (ONJ), a condition termed bisphosphonate-related OHJ. Other antiresorptive drugs have been implicated in the development of OHJ, hence the new term antiresorptive drug–related ONJ. The underlying pathogenesis remains unclear, and no definite diagnosis or cure has been established for this debilitating condition. This article reviews some of the most common antiresorptive drugs with their associated risks of ONJ and the current understanding of the pathogenesis ONJ, and summarizes current clinical guidelines.
Key points
- •
Nitrogen-containing and non–nitrogen-containing bisphosphonates have been implicated in the development of osteonecrosis of the jaw, a condition termed bisphosphonate-related osteonecrosis of the jaw.
- •
Other antiresorptive drugs have recently been implicated in the development of osteonecrosis of the jaw, hence the new term antiresorptive drug–related osteonecrosis of the jaw (ARONJ).
- •
Cofactors such as infection, diabetes, steroids, cancer, and chemotherapy may direct immune suppression and potentiate ARONJ development sooner.
- •
The risk of ARONJ is associated with the type of antiresorptive medication, route, and dosage.
Introduction
Osteonecrosis of the jaw (ONJ) is a debilitating bone disorder of the jaw and is defined by the advisory tasks forces from both the American Association of Oral and Maxillofacial Surgeon (AAOMS) and the American Society for Bone and Mineral Research (ASBMR) as the persistence of exposure of bone in the oral cavity for more than 8 weeks refractory to treatment, current or previous history of bisphosphonate (BP) use, no evidence of malignancy, and no prior radiotherapy to the affected region. Antiresorptive drug–related ONJ (ARONJ) is a recent concept adapted and recommended by the 2008 American Dental Association (ADA) Council on Scientific Affairs. The ADA council recommended that all cases related to the administration of antiresorptive agents be termed antiresorptive agent–induced ONJ. This recommendation encompasses all antiresorptive drugs that could cause development of ONJ. Many patients are being treated with antiresorptive or antiremodeling agents such as hormonal replacement therapy, selective estrogen receptor modulators, calcitonin (direct inhibitor of osteoclasts), BPs, or the monoclonal antibody (eg, denosumab).
At present, ARONJ development has been associated with the use of BPs and anti–receptor activated nuclear factor KB ligand (anti-RANKL) monoclonal antibody such as denosumab. It has been postulated that ARONJ results from reduced bone turnover caused by the antiresorptive drugs, by which denosumab seems to have an equal or greater extent of bone turnover suppression than BP. Besides BP and anti-RANKL drugs, other antiresorptive agents have a low risk of ARONJ, which may in part be because they do not suppress bone turnover by more than 50%.
Antiresorptive Drugs Associated with ONJ
BP
BPs have been widely used as antiresorptive agents for management of skeletal-related events in neoplasia, hypercalcemia of malignancy, osteoporosis, Paget disease, osteogenesis imperfecta, and fibrous dysplasia. BP has been linked to the development of ARONJ. The currently accepted theory for the development ARONJ is through direct and indirect effects on bone turnover via apoptosis of osteoclasts. BP is the synthetic analogue of inorganic pyrophosphate, containing a phosphorus-carbon-phosphorus (PCP) backbone and a variable side chain (nitrogen or non-nitrogen) that determines the potency for inhibition of bone resorption.
BPs that lack a nitrogen functional group (etidronate, clodronate, tiludronate) condense to form the nonhydrolyzable analogue of ATP, which inhibits ATP-dependent intracellular enzyme, resulting in osteoclast cell death. In contrast, the nitrogen-containing BP (pamidronate, ibandronate, zoledronate, risedronate, alendronate) inhibit the activity of farnesyl diphosphate synthase, which is a key enzyme in the mevalonate pathway. Inhibition of this enzyme creates an intracellular deficiency of geranylgeranyl diphosphate and farnesyl diphosphate, which are both required for prenylation of small signaling proteins with GTPase activity. This process results in dysfunctional osteoclasts and eventually apoptosis. The nitrogen-containing BP has a higher potency and thus is effective in therapeutic management of skeletal-related events in cancer but also results in a higher risk ONJ. Zoledronic acid is the most potent BP (500–1000 times more potent than pamidronate) and was the first drug approved for use in all solid tumors with bone metastasis such as breast cancer, prostate, multiple myeloma, and lung cancer. Intravenous (IV) BP exposure in the setting of managing malignancy remains the major risk factor for ARONJ, whereas treatment with oral BP therapy is at a considerably lower risk for ARONJ, possibly because IV administration of BP results in a higher skeletal accumulation caused by the high mineral-binding affinity and is also associated with earlier onset of ARONJ than oral BP.
Anti-RANK ligand: denosumab
Denosumab is an antiresorptive agent that also inhibits osteoclast-mediated bone resorption. Denosumab has US Food and Drug Administration approval for the treatment of osteoporosis and skeletal-related events (SREs) in patients with cancer. Prolia (Amgen) was approved for treatment of osteoporosis and Xgeva (Amgen) for prevention of skeletal-related events in patients with bone metastases from solid tumors (Prolia/Xgeva [denosumab], prescribing information. Amgen, Thousand Oaks, CA; 2010). Denosumab works in a different pathway than BP in that it is a human monoclonal antibody (immunoglobulin G2) that inhibits receptor-activated nuclear factor KB ligand (RANKL) by mimicking the effect of osteoprotegerin on RANKL. RANKL plays an important role in bone remodeling. It is a cytokine that is expressed on many cells including osteoblasts, bone marrow stomal cells, and immune cells. It plays a vital role in osteoclast cell function, activation, and differentiation and thus decreases bone turnover. Because RANKL is expressed on the subset of T and B cells, there is a possibility that denosumab may be immunosuppressive.
In the FREEDOM (Fracture Reduction Evaluation of Denosumab in Osteoporosis every 6 Months) trial of 7000 patients with osteoporosis, there was a significant reduction of fractures in the treatment group; however, no cases of ARONJ were observed. Denosumab significantly increases bone mass density by reducing osteoclast numbers and other parameters of bone turnover including levels of the bone resorption marker serum C-telopeptide. Reduced turnover significantly increases bone mass density. Besides ARONJ, other adverse effects associated with denosumab include hypocalcemia, pancreatitis, and severe infection.
Differences between BP and denosumab
Both BP and denosumab are associated with development of ARONJ and are approved for postmenopausal osteoporosis in women at increased risk of fracture and for the treatment of bone loss associated with cancer. Denosumab has several advantages, including better tolerability, ease of subcutaneous injection, and decreased incidence of nephrotoxicity compared with BP. In terms of drug half-life, denosumab has an advantage compared with BP, with a shorter half-life of 25.4 days, compared with 10 to 12 years for BP. In a phase II trial, denosumab suppressed bone resorption markers including urinary collagen type I cross-linked N-telopeptide (NTx) within 24 hours after initial dose and a greater reduction of these markers by 74% compared with 63% in BP-treated patients. Denosumab has a shorter half-life and is therefore reversible. It is eliminated via the immunoglobin clearance pathway in the reticuloendothelial system, which makes it less nephrotoxic and possibly the drug of choice for renal patients or diseases with the propensity toward renal dysfunction, such as renal cell cancer and prostate cancer. In the phase III clinical trials of 5677 patients with bone metastasis, the risk of ARONJ was similar for both BP with 37 (1.3%) cases (zoledronic acid) and denosumab with 52 (1.8%) cases.
Introduction
Osteonecrosis of the jaw (ONJ) is a debilitating bone disorder of the jaw and is defined by the advisory tasks forces from both the American Association of Oral and Maxillofacial Surgeon (AAOMS) and the American Society for Bone and Mineral Research (ASBMR) as the persistence of exposure of bone in the oral cavity for more than 8 weeks refractory to treatment, current or previous history of bisphosphonate (BP) use, no evidence of malignancy, and no prior radiotherapy to the affected region. Antiresorptive drug–related ONJ (ARONJ) is a recent concept adapted and recommended by the 2008 American Dental Association (ADA) Council on Scientific Affairs. The ADA council recommended that all cases related to the administration of antiresorptive agents be termed antiresorptive agent–induced ONJ. This recommendation encompasses all antiresorptive drugs that could cause development of ONJ. Many patients are being treated with antiresorptive or antiremodeling agents such as hormonal replacement therapy, selective estrogen receptor modulators, calcitonin (direct inhibitor of osteoclasts), BPs, or the monoclonal antibody (eg, denosumab).
At present, ARONJ development has been associated with the use of BPs and anti–receptor activated nuclear factor KB ligand (anti-RANKL) monoclonal antibody such as denosumab. It has been postulated that ARONJ results from reduced bone turnover caused by the antiresorptive drugs, by which denosumab seems to have an equal or greater extent of bone turnover suppression than BP. Besides BP and anti-RANKL drugs, other antiresorptive agents have a low risk of ARONJ, which may in part be because they do not suppress bone turnover by more than 50%.
Antiresorptive Drugs Associated with ONJ
BP
BPs have been widely used as antiresorptive agents for management of skeletal-related events in neoplasia, hypercalcemia of malignancy, osteoporosis, Paget disease, osteogenesis imperfecta, and fibrous dysplasia. BP has been linked to the development of ARONJ. The currently accepted theory for the development ARONJ is through direct and indirect effects on bone turnover via apoptosis of osteoclasts. BP is the synthetic analogue of inorganic pyrophosphate, containing a phosphorus-carbon-phosphorus (PCP) backbone and a variable side chain (nitrogen or non-nitrogen) that determines the potency for inhibition of bone resorption.
BPs that lack a nitrogen functional group (etidronate, clodronate, tiludronate) condense to form the nonhydrolyzable analogue of ATP, which inhibits ATP-dependent intracellular enzyme, resulting in osteoclast cell death. In contrast, the nitrogen-containing BP (pamidronate, ibandronate, zoledronate, risedronate, alendronate) inhibit the activity of farnesyl diphosphate synthase, which is a key enzyme in the mevalonate pathway. Inhibition of this enzyme creates an intracellular deficiency of geranylgeranyl diphosphate and farnesyl diphosphate, which are both required for prenylation of small signaling proteins with GTPase activity. This process results in dysfunctional osteoclasts and eventually apoptosis. The nitrogen-containing BP has a higher potency and thus is effective in therapeutic management of skeletal-related events in cancer but also results in a higher risk ONJ. Zoledronic acid is the most potent BP (500–1000 times more potent than pamidronate) and was the first drug approved for use in all solid tumors with bone metastasis such as breast cancer, prostate, multiple myeloma, and lung cancer. Intravenous (IV) BP exposure in the setting of managing malignancy remains the major risk factor for ARONJ, whereas treatment with oral BP therapy is at a considerably lower risk for ARONJ, possibly because IV administration of BP results in a higher skeletal accumulation caused by the high mineral-binding affinity and is also associated with earlier onset of ARONJ than oral BP.
Anti-RANK ligand: denosumab
Denosumab is an antiresorptive agent that also inhibits osteoclast-mediated bone resorption. Denosumab has US Food and Drug Administration approval for the treatment of osteoporosis and skeletal-related events (SREs) in patients with cancer. Prolia (Amgen) was approved for treatment of osteoporosis and Xgeva (Amgen) for prevention of skeletal-related events in patients with bone metastases from solid tumors (Prolia/Xgeva [denosumab], prescribing information. Amgen, Thousand Oaks, CA; 2010). Denosumab works in a different pathway than BP in that it is a human monoclonal antibody (immunoglobulin G2) that inhibits receptor-activated nuclear factor KB ligand (RANKL) by mimicking the effect of osteoprotegerin on RANKL. RANKL plays an important role in bone remodeling. It is a cytokine that is expressed on many cells including osteoblasts, bone marrow stomal cells, and immune cells. It plays a vital role in osteoclast cell function, activation, and differentiation and thus decreases bone turnover. Because RANKL is expressed on the subset of T and B cells, there is a possibility that denosumab may be immunosuppressive.
In the FREEDOM (Fracture Reduction Evaluation of Denosumab in Osteoporosis every 6 Months) trial of 7000 patients with osteoporosis, there was a significant reduction of fractures in the treatment group; however, no cases of ARONJ were observed. Denosumab significantly increases bone mass density by reducing osteoclast numbers and other parameters of bone turnover including levels of the bone resorption marker serum C-telopeptide. Reduced turnover significantly increases bone mass density. Besides ARONJ, other adverse effects associated with denosumab include hypocalcemia, pancreatitis, and severe infection.
Differences between BP and denosumab
Both BP and denosumab are associated with development of ARONJ and are approved for postmenopausal osteoporosis in women at increased risk of fracture and for the treatment of bone loss associated with cancer. Denosumab has several advantages, including better tolerability, ease of subcutaneous injection, and decreased incidence of nephrotoxicity compared with BP. In terms of drug half-life, denosumab has an advantage compared with BP, with a shorter half-life of 25.4 days, compared with 10 to 12 years for BP. In a phase II trial, denosumab suppressed bone resorption markers including urinary collagen type I cross-linked N-telopeptide (NTx) within 24 hours after initial dose and a greater reduction of these markers by 74% compared with 63% in BP-treated patients. Denosumab has a shorter half-life and is therefore reversible. It is eliminated via the immunoglobin clearance pathway in the reticuloendothelial system, which makes it less nephrotoxic and possibly the drug of choice for renal patients or diseases with the propensity toward renal dysfunction, such as renal cell cancer and prostate cancer. In the phase III clinical trials of 5677 patients with bone metastasis, the risk of ARONJ was similar for both BP with 37 (1.3%) cases (zoledronic acid) and denosumab with 52 (1.8%) cases.
Epidemiology
Since 2003, ARONJ has been reported as a serious side effect of BP treatment. The reported rate of incidence for ARONJ from a population-based study is 0.8% to 1.5% for IV BP and 0.01% to 0.04% for oral BP. However, dental extractions or trauma may significantly increase the BP risk of ARONJ from 1 in 10,000 and 1 in 100,000 to a risk of 1 in 300 ( Table 1 ). It is recognized that 60% of cases occurred following a tooth extraction or other dentoalveolar surgery versus the remaining cases, which occur spontaneously. It is estimated that the incidence of ARONJ in patients with malignancy ranges from 1% to 10%. A systematic review of 368 reported cases of ARONJ from 2003 to 2006 revealed that 94% of these patients were treated with IV BP (primarily pamidronate and zoledronate), and 85% of the patients had either multiple myeloma or metastatic breast cancer, whereas the remaining patients were on oral BP for osteoporosis or Paget disease of bone. The oncologic doses for BP are 10 to 12 times higher than osteoporosis doses and are usually given in combination with steroids. The cumulative effect was higher for zoledronate compared with pamidronate, with a 1% versus 0% risk, respectively, within the first year, and a 21% versus 4% risk, respectively, after 3 years of treatment. The estimated incidence of ARONJ in patients receiving IV BP for malignant disease ranges from 0.8% to 12%, which is 900 times higher than that of the general patient with osteoporosis. In a case-controlled study by Wessel and colleagues, patients with cancer who had received zoledronate showed a significant 30-fold increase in their risk to develop ARONJ. Incidence of ARONJ is significantly higher in patients with cancer compared with patients with osteoporosis. In a study of risk of ARONJ among patients with different types of cancer (breast cancer, prostate cancer, multiple myeloma), the International Myeloma Association study showed that patients with cancer with multiple myeloma were more likely to have a higher risk of ARONJ than breast or prostate cancer. In a retrospective cohort study by Tennis and colleagues, the incidence of ARONJ in the cancer cohort group was 5.3% among IV BP and 0.15% in the osteoporosis group using oral BP. Patients with multiple myeloma had an incidence 4.5 times that of patients with breast cancer. Among patients with cancer, the incidence of ARONJ was reported as 3.8%, 2.5%, and 2.9% for multiple myeloma, breast cancer, and prostate cancer, respectively. In the patients with cancer treated with BP, the incidence rates for ARONJ were related to (1) length of exposure to the drug, (2) history of dental procedures, (3) number of treatment cycles, and (4) delivery method (IV or oral).
| Medical Comorbidities | Dental Comorbidities |
|---|---|
| Cancer | Periodontitis |
| Anemia | Infection |
| Smoking | Failed root canal therapy |
| Chemotherapy | Extraction |
| Radiation | Implants |
| Steroid | Trauma |
| Rheumatoid arthritis | Periodontal surgery |
| Antimetabolite medications | Apicoectomy |
| Diabetes | — |
| Obesity | — |
| Immunosuppression | — |
| Age | — |
| Alcohol | — |
| Malnutrition | — |
Worldwide incidence
The association between BP and ARONJ has been well established. With the increased rate of aging of the population, the World Health Organization predicts that people older than 65 years will comprise 20% of the world’s population by 2030. More than 24 million prescriptions for BP were issued in the United States and more than 190 million internationally. A postal survey of oral surgeons and members of the Commonwealth of Australia Adverse Drug Reaction Committee indicates that the rate of ARONJ for inpatients receiving alendronate was between 1 per 2260 and 1 per 8470 patients (0.01%–0.04%).
Clinical parameters
Diagnostic Guidelines and Staging of ARONJ
ARONJ can be a debilitating complication of BP therapy. The diagnostic criteria for ARONJ were formulated by the advisory task forces from AAOMS and the ASBMR in 2007, and revised in 2009. The diagnostic criteria for ARONJ include (1) an exposed, necrotic bone in the maxillofacial region that has persisted for more than 8 weeks; (2) current or previous history of BP use; and (3) no history of radiation therapy to the head and neck area. In addition to exposed nonhealing bone, other signs and symptoms may be present in suspected cases of ARONJ including pain, swelling, paresthesia, suppuration, nonhealing soft tissue ulcerations, sinus tracts, mobile or periodontally involved teeth, and radiographic variability including radiolucencies or radiopacities. Lesions can occur spontaneously but most cases of ARONJ occur after dental extraction or traumatic insult.
The revised guideline in 2009 was established to include patients with stage 0 disease, characterized as having no evidence of exposed necrotic bone. The current AAOMS guideline for ARONJ classifies the condition into 4 stages based on clinical findings to include stage 0 patients, who have no evidence of bone necrosis with nonspecific clinical findings and symptoms; stage 1 is characterized by the presence of exposed and necrotic bone, without evidence of infection; stage 2 patients have clinically exposed/necrotic bone with evidence of infection (pain, erythema, with or without purulent drainage); stage 3 patients have severely exposed and necrotic bone with severe infection extending beyond the alveolar bone region, osteolysis extending to the inferior border of the mandible or sinus floor, a predisposition to pathologic fracture, and oral-antral or oral-nasal communication. Several reports of a clinical variant of ARONJ have recently been described, in which clinical features reported persistent bone pain, bone enlargement with gingival swelling, but no evidence of dental disease or exposure of bone. Hutchinson and colleagues reported that 30 patients out of 1005 presented no evidence of bone exposure and 10 of the 30 patients were stage 0 with radiographic changes of osteosclerosis in the symptomatic area. Such cases present a dilemma for the clinician both in diagnosis and management of ARONJ. Exposed necrotic bone is an important clinical characteristic of ARONJ. In these variant cases, the absence of the clinical signs of ARONJ can lead to late diagnosis, prolonged disease course, and a condition that is refractory to treatment. Patel and colleagues proposed a modification of the current staging system and treatment guidelines for the management of the variant form, nonexposed BP-related ONJ. Patel and colleagues also proposed to add to the current AAOMS staging guideline the term nonexposed to each stage to accurately reflect the clinical presentation of the ARONJ.
Imaging
ARONJ is a well-defined clinical disease with consistent radiographic findings to include osteosclerosis, osteolysis, dense woven bone, thickened lamina dura, subperiosteal bone deposition, and failure of postsurgical remodeling. Panoramic radiography is routinely used because it is one of the least expensive modalities for viewing the jaw. On the panoramic radiograph, bony sequestra, osteonecrosis, and metastatic lesion(s) are readily identifiable. In ARONJ diagnosis, panoramic imaging can be used as an initial study for evaluating the jaw, although it may not reveal any significant changes for early stage ARONJ, but late stages may resemble periapical inflammatory lesions or osteomyelitis.
Computed tomography (CT) is another modality that can be used for differential diagnosis. CT may reveal a higher bone density with bony sequestration in advanced ARONJ cases. Cone beam CT gives details on thickness of cortex, integrity and bone marrow involvement, cancellous bone mineral density, and irregularities after tooth extraction.
Magnetic resonance imaging (MRI) can be useful in assessing osteonecrosis or ischemia with the use of contrast; however, it may give false-positive results. The histopathologic changes of necrotic bone are comparable and are depicted similarly by MRI. MRI can show bone marrow changes associated with edema or inflammation resulting from an increase in water content, which replaces the normal fatty bone marrow. On MRI, these changes in marrow are seen as low signal intensity on T1-weighted imaged and a high signal intensity on T2-weighted images. There is speculation that marrow edema is not a part of the pathogenesis of ARONJ as seen in avascular bone necrosis and MRI may be of limited use in the diagnosis of ARONJ.
Bone scintigraphy is mostly used in diagnosis and management of metastatic disease. It can provide information regarding local metabolic and vascular changes, is highly sensitive to detecting bony involvement, and facilitates earlier diagnosis than conventional radiographs. In a retrospective study conducted at Kaiser by O’Ryan and colleagues, 35 patients with previous plantar technetium (Tc) 99 methylene diphosphate or hydroxymethylene diphosphonate bone scintigraphy, 23 (65.7%) showed positive tracer uptake in the areas that later developed ARONJ. 18 F-fluorodeoxyglucose positron emission tomography (FDG-PET)/CT is another diagnostic tool used in the evaluation of patients with metastatic disease and can also be used to identify subclinical areas of hypermetabolic activity in the jaw of patients with ARONJ. However, definitive diagnosis can only be determined by biopsy because FDG-PET cannot differentiate between malignancy and ARONJ.
Stay updated, free dental videos. Join our Telegram channel
VIDEdental - Online dental courses
