The "Scintigraphic Flip": A Visual Warning Sign of Impending Hematologic Toxicity.

We report a 55-year-old man with metastatic castration-resistant prostate cancer who developed a dramatic "scintigraphic flip" after the second cycle of ¹⁷⁷Lu-PSMA therapy. Post-therapy SPECT and follow-up ¹⁸F-PSMA PET/CT showed increased diffuse marrow uptake with paradoxically reduced salivary-gland and liver activity. Despite improved bone pain, reduced analgesic use, and no clinical or laboratory warning signs, this silent redistribution preceded grade III thrombocytopenia and marked anemia, hospitalization for transfusion and supportive care, and death. This case suggests that interval PSMA PET/CT, particularly in selected high-risk patients, may help identify occult marrow redistribution and support individualized dose adaptation.