PT - JOURNAL ARTICLE AU - Dittmann, Helmut AU - Kaltenbach, Sabine AU - Weissinger, Matthias AU - Fiz, Francesco AU - Martus, Peter AU - Pritzkow, Maren AU - Kupferschlaeger, Juergen AU - la Fougère, Christian TI - The Prognostic Value of Quantitative Bone SPECT/CT Before <sup>223</sup>Ra Treatment in Metastatic Castration-Resistant Prostate Cancer AID - 10.2967/jnumed.119.240408 DP - 2021 Jan 01 TA - Journal of Nuclear Medicine PG - 48--54 VI - 62 IP - 1 4099 - http://jnm.snmjournals.org/content/62/1/48.short 4100 - http://jnm.snmjournals.org/content/62/1/48.full SO - J Nucl Med2021 Jan 01; 62 AB - Radiolabeled bisphosphonates such as 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) typically show intense uptake in skeletal metastases from metastatic castration-resistant prostate cancer (mCRPC). Extensive bone involvement is regarded as a risk factor for mCRPC patients treated with 223Ra-dichloride (223Ra). The aim of this study was to quantify 99mTc-DPD uptake by means of SPECT/CT before 223Ra and compare the results with the feasibility of treatment and overall survival (OS). Methods: Sixty consecutive mCRPC patients were prospectively included in this study. SPECT/CT of the central skeleton covering the skull to the mid-femoral level was performed before the first cycle of 223Ra. The bone compartment was defined by means of low-dose CT. Emission data were corrected for scatter, attenuation, and decay supplemented by resolution recovery using dedicated software. The Kaplan–Meier estimator, U test, and Cox regression analysis were used for statistics. Results: Total 99mTc-DPD uptake of the central skeleton varied between 11% and 56% of injected dose (%ID) or between 1.8 and 10.5 %ID/1,000 mL of bone volume (%ID/L). SUVmean ranged from 1.9 to 7.4, whereas the SUVmax range was 18–248. Patients unable to complete 223Ra treatment because of progression and/or cytopenia (n = 23) showed significantly higher uptake (31.9 vs. 25.4 %ID and 6.0 vs. 4.7 %ID/L; P &lt; 0.02). OS after 223Ra (median, 15.2 mo) was reduced to 7.3 mo in cases of skeletal uptake that was 26 %ID or higher, as compared with 30.8 mo if lower than 26 %ID (P = 0.008). Similar results were obtained for %ID/L and SUVmean. SUVmax did not correlate with survival. %ID/L was identified as an independent prognostic factor for OS (hazard ratio, 1.381 per unit), along with number of previous treatment lines. Conclusion: Quantitative SPECT/CT of bone scans performed at baseline is prognostic for survival in mCRPC patients treated with 223Ra.