Small Cell Transformation of Metastatic Prostate Adenocarcinoma Diagnosed by Dual-Tracer PET/CT (68Ga-PSMA and 18F-FDG): Potential Clinical Utility in Therapeutic Decision Making and Treatment Monitoring

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FIGURE 1.
(A) ⁶⁸Ga-PSMA PET/CT (March 2016) showing intensely avid prostatic and D9 vertebral lesions, faint uptake in large pelvic mass, and central necrosis infiltrating prostate and rectum (arrow). (B) ⁶⁸Ga-PSMA PET/CT (December 2016) showing significant reduction of pelvic mass and decreased uptake in prostatic lesion.
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FIGURE 2.
(A) ⁶⁸Ga-PSMA PET/CT demonstrating intense avidity in multiple dorsal and lumbar vertebrae (pink arrows), bilaterally in ribs, and in pelvic bone, with nonavid left pelvic soft-tissue (red arrows) and penile shaft lesions. ¹⁸F-FDG PET/CT (B and C) showed intense skeletal lesions similar to ⁶⁸Ga-PSMA, intensely avid left pelvic soft-tissue lesion (SUV_max, 45; 3.0 × 2.2 cm; red arrow) and ¹⁸F-FDG–avid penile shaft lesion (SUV_max, 44; 2.5 × 2.0 cm; green arrow). Follow-up ⁶⁸Ga-PSMA-PET/CT (A) showed decrease in uptake in skeletal lesions; ¹⁸F-FDG PET/CT (B, D, and E) showed decrease in size and uptake in left pelvic soft-tissue lesion (red arrow; SUV_max, 6; 1.5 × 1.7 cm), indicating response to intensity-modulated radiation therapy, and untreated penile shaft lesion demonstrated persistence of ¹⁸F-FDG uptake (green arrow).