Predicting the Prognosis of Prostate Cancer Bone Metastasis Using the Bone Scan Index and Hot Spots Calculated Using VSBONE<sup>Ⓡ</sup> Bone Scan Index from Tc-99m-Hydroxymethylene Diphosphonate Bone Scintigraphy

<b><i>Introduction:</i></b> The bone scan index (BSI) is widely used as a quantitative indicator of bone metastasis, therapeutic effect assessment, and prognosis prediction in prostate cancer. However, the BONE NAVI, which calculates BSI, only supports bone scintigraphy using Tc-99m-methylene diphosphonate. We developed the VSBONE^Ⓡ BSI, which calculates BSI from bone scintigraphy using Tc-99m-hydroxymethylene diphosphonate (HMDP). The purpose of this study was to demonstrate that the BSI calculated using VSBONE^Ⓡ BSI and hot spots (HS), which indicates the number of abnormal accumulations, are useful prognostic factors for patients with prostate cancer bone metastasis, similar to BONE NAVI. <b><i>Methods:</i></b> We analyzed 322 patients who underwent bone scintigraphy for prostate cancer bone metastasis at our hospital. Initial bone scintigraphy was performed using Tc-99m-HMDP. All cases were retrospectively examined for their outcome and time to the final outcome. The results obtained were compared with the BSI and HS calculated using VSBONE^Ⓡ BSI. <b><i>Results:</i></b> When the patients were divided into two groups, HS &#x3e;2 and HS ≤2, the HS ≤2 group had a significantly longer survival time (<i>p</i> &#x3c; 0.001). In addition, when divided into two groups, BSI &#x3e;0.46 and BSI ≤0.46, the survival time of the BSI ≦0.46 group was significantly longer (<i>p</i> &#x3c; 0.001). <b><i>Conclusion:</i></b> BSI and HS obtained using VSBONE^Ⓡ BSI may be useful as prognostic predictors, similar to those obtained using BONE NAVI.