Reply: Bone Scintigraphy and SPECT/CT in Bisphosphonate-Induced Osteonecrosis of the Jaw

REPLY: We thank Fabbricini and colleagues for their letter and appreciate their comments on our study (1).

The aim of our study was more to assess the possible clinical utility of hybrid SPECT/CT for ^99mTc-methylene diphosphonate (MDP) imaging of osteonecrosis of the jaw than to differentiate between metastasis and osteonecrosis of the jaw.

Because of the well-known lack of specificity of bone scanning, all 15 patients underwent an accurate clinical evaluation, which, in every case, supported the suspicion of osteonecrosis of the jaw.

Fourteen patients had exposed bone (8 at the time of the scintigraphic study), and among these 14, 4 had multiple myeloma. Biopsy excluded metastatic involvement of the jaw and confirmed osteonecrosis of the jaw in all cases.

The hybrid SPECT/CT findings correlated with the clinical and histologic findings.

The 4 patients with multiple myeloma did not undergo bone scanning for staging, since ^99mTc-MDP imaging is known to have poor sensitivity in this disease except when used to evaluate therapeutic response or to detect early osteosclerotic reactions.

SPECT/CT increased the accuracy of conventional imaging by allowing differentiation between the osteonecrotic core and viable bone in 8 patients. SPECT/CT also provided important information for treatment planning. Catalano et al. (2) showed that in differentiating osteonecrosis of the jaw from myeloma osteolysis, an imaging technique such as sestamibi scintigraphy, with a tracer taken up by neoplastic cells and not by inflammatory ones, may be more helpful than an imaging procedure such as ¹⁸F-FDG PET, with a tracer taken up also by inflammation.

They raise the interesting question of whether ^99mTc-sestamibi SPECT/CT coupled with ^99mTc-MDP SPECT/CT is as accurate as ^99mTc-sestamibi SPECT coupled with ¹⁸F-FDG PET. Regarding this question, we fully agree with the paper by Pazianas et al. (3), who suggested that because our group obtained satisfying results using a basilar SPECT/CT technology, better results might be achieved using hybrid systems with higher resolution and greater diagnostic capability.