PMC9195502_01
FDG PET-Scan before and after radium-223 treatment. The images circled in red depict a decrease of FDG uptake in axial skeletal metastases, reflecting a response to treatment. The images circled in green illustrate medullary regeneration in humerus and femur after treatment by showing homogeneization of FDG uptake. The images circled in yellow illustrate a decrease of FDG uptake in the right humeral head. For example, the Maximum Standardized Uptake Value (SUVmax) decreased of 59.2% in the at the 10th dorsal vertebra (12.38 in pre- to 5.05 in post- radium-223) and of 63.6% in the sacrum (14.91 in pre- to 5.43 in post-radium-223). The SUVmax of the Aorta bloodpool was 2.76 in pre- and 2.25 in post-radium-223 (-18%). The SUVmax in normal liver (reference) was 2.14 in pre- and 2.20 in post-radium-223 (+2.8%).
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However, a decrease in FDG uptake was observed in all bone metastatic lesions ( Figure 1 ) that were previously described; for example, we observed a metabolic decrease of 59% in the 10th dorsal vertebra (with maximum standardized uptake value (max.
99mTc-HDP bone scan before and after radium-223 treatment. The images circled in red depict a decrease of 99Tc uptake reflecting decreased metastatic activity. The images circled in green show an increase in bone uptake in the right humeral head reflecting bone reconstruction (given a decrease of FDG uptake on PET-CT). The images circled in blue illustrate a global decrease in 99Tc uptake of the axial skeleton.
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There was a discrepancy between FDG metabolism decrease and 99Tc uptake increase in the humeral head ( Figure 2 ), which likely reflects reparative bone associated with treatment response.
Lumbar spine CT-scan before and after Radium-223 treatment. The CT-scan performed after Radium-223 shows bone formation in lumbar vertebras.
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CT of the column showed hyperdensities of bone metastases, reflecting increased bone formation on treatment ( Figure 3 ). CA15.3 level increased from 941 kU/L at baseline to 1135 kU/L after radium-223 which is attributed to the progressive liver and nodal metastases.
Timeline.
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The timeline is summarized in  Figure 4 .