Serum VEGF levels as predictive marker of bisphosphonate-related osteonecrosis of the jaw

Recent studies have been reported that angiogenesis suppression may play a role in developing bisphosphonate-related osteonecrosis of the jaw (B-ONJ). According to these evidence we evaluated the role of VEGF as predictive marker of B-ONJ onset. Of the 81 patients, 6 developed B-ONJ following bisphosphonate treatment. These patients showed a strongest decrease in VEGF circulating levels at day 7 and at day 21 after the first administration. These data demonstrated for the first time that the anti-angiogenic properties of bisphosphonates are directly linked to B-ONJ pathogenesis and serum VEGF levels could represent an effective early predictive marker.

Bisphosphonate-related osteonecrosis of the jaw (B-ONJ) is defined as non-healing exposed bone in the mandible or maxilla persisting for more than 8 weeks in a patient with no history of radiation therapy on the jaws who has taken or is currently taking a bisphosphonate. B-ONJ is a wellknown adverse effect reported in about 5% of patients with cancer receiving high-dose intravenous bisphosphonates [1].
B-ONJ pathogenesis is still uncertain and under debate; bisphosphonates indeed act on a wide variety of cells, possibly increasing susceptibility to infections in the oral cavity and impairing mucosal healing acting on monocyte differentiation, angiogenesis or both [1].
Recently, several cases of exposed bone in the mandible, with a very close clinical presentation to B-ONJ, have been reported in cancer patients treated with bevacizumab, a recombinant human monoclonal antibody that binds to vascular endothelial growth factor (VEGF) and inhibits angiogenesis [2,3]. According to popular hypothesis, angiogenesis suppression may indeed play a role in B-ONJ [4], even though evidences are currently lacking. Notably, vascular impairment is considered to be crucial in the pathogenesis of other bisphosphonate-unrelated osteonecrosis (e.g. osteoradionecrosis, avascular necrosis of the hip and corticosteroid-induced osteonecrosis).
Notably, beside known antiresorptive, immunomodulating and direct antitumor actions, bisphosphonates are now considered to be also anti-angiogenic drugs: in our three previous works we showed the reduction of circulating VEGF in cancer patients suffering from bone metastases after treatment with either zoledronic acid (standard schedule or metronomic administration) or pamidronate [5][6][7].
To the best of our knowledge, this is the first evidence that the anti-angiogenic properties of bisphosphonates are directly linked to B-ONJ pathogenesis. If confirmed, serum VEGF levels at day 7 and 21 after the first administration of intravenous bisphosphonate could represent an effective early predictive marker of B-ONJ.Finally, we are aware that these data come from a very small retrospective analysis, but their potential impact in clinical practice warrants prospective studies and extensive validation by the entire medical community.

Competing interests
The authors declare that they have no competing interests.
Authors' contributions BV conceived the study and gave substantial contribution to data analysis and interpretation; AN have been involved in drafting and revising the manuscript; AZ, MI and FP have been involved in the acquisition, analysis and interpretation of data; DS, NP, VD and GT have been involved in revising critically the manuscript. All authors read and approved the final manuscript.