Detection of Peritoneal Carcinomatosis in Prostate Cancer via 99m Tc-HYNIC-PSMA-11 Scintigraphy.

We present a 73-year-old man with de novo metastatic prostate cancer who had received chemotherapy and androgen deprivation therapy (ADT). An increase in his serum prostate-specific antigen (PSA) level during ADT prompted a referral for restaging. A 99m Tc-HYNIC-PSMA-11 scintigraphy was conducted, which revealed uptake in the peritoneal cavity that was initially interpreted as normal intestinal excretion on the whole body scan but was later clarified through SPECT/CT imaging. This case underscores the potential of functional imaging, even conventional methods, to surpass anatomical imaging techniques such as CT scans, which have limited soft tissue resolution, in assessing peritoneal involvement.