Diagnosis and semiquantification of osteonecrosis of the jaw by bone scan index on bone scintigraphy.

Abstract

e639 Background: Bone management is extremely important for maintaining QOL of prostate or renal cancer patients with bone metastasis. Physicians often administrate bone modifying agents (BMA), zoledronic acid or denosumab, to prevent skeletal-related event and bone pain for such patients. However, osteonecrosis of the jaw (ONJ) is one of sever adverse events of BMA (Medication-related ONJ; MRONJ). The early detection and follow-up of ONJ is extremely important issue. In order to achieve this issue, we utilized bone scintigraphy and a computer-aided diagnosis using a bone scan index (BSI). Methods: A total of 22 patients with either prostate cancer or renal cancer (27 lesions) diagnosed with MRONJ after treatment with BMA were investigated. Median age was 72.5 years (range 52-82 years). The primary disease was prostate cancer (81.8%), renal cancer (18.2%). Regarding the treatment, 86.4% of the patients were treated with bisphosphonate drugs, none in denosumab, and both in 13.6%, respectively. The median duration of medication was 33 months (range 7-70 months) by the time of MRONJ diagnosis. All patients underwent Tc-99m methylene diphosphonate bone scintigraphy. Bone uptake in the jaw was analyzed using BSI, which was calculated by BONENAVI (FUJIFILM RI Pharma, Japan; EXINIbone, EXINI Diagnostics, Sweden). Significant hot spots were manually selected according to both serial scintigraphic images and dental records, and the fraction of them to the entire skeleton was referred as BSI of the jaw (BSIJ). The level of BSIJ was evaluated in comparison with stage of ONJ and inflammation marker, C-reactive protein (CRP). Results: The median BSIJ of lesions was 0.14 (range 0.00-0.43) at the time of MRONJ diagnosis. If MRONJ is not treated appropriately, BSIJ tended to increase during treatment with BMA. When patients were classified according to their clinical stages of MRONJ, higher stage MRONJ lesions had significantly higher BSIJ (p < 0.01). In addition, BSIJ was correlated with CRP. Conclusions: Evaluation of BSIJ using BONENAVI on bone scintigraphy was helpful for early detection and follow-up of MRONJ. Furthermore, increased BSIJ on bone scintigraphy were related to CRP and stage of ONJ.