Synchronous Colorectal and Prostate Cancer: Dual PET/CT Approach for Detecting and Distinguishing Metastatic Patterns

Prostate cancer (PC) and colorectal cancer (CRC) are two of the leading causes of cancer-related mortality. The incidence of synchronous neoplasms in patients with CRC is increasing, though synchronous PC and CRC remains a rare occurrence in clinical practice. Early diagnosis, accurate staging, and characterization of tumors are essential for selecting patient-tailored therapy. The origin of metastatic disease in synchronous cases presents a challenge for conventional imaging modalities, but advances in molecular imaging have addressed this limitation. Positron emission tomography/computed tomography (PET/CT) is now the preferred modality for assessing synchronous cases. The authors present a 72-year-old male patient with the rare occurrence of two coexisting primary cancers. At first, fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) PET/CT detected the first colorectal primary tumor extension along with evidence of heterogeneous ¹⁸F-FDG activity within an enlarged prostate, warranting further evaluation. Subsequently, gallium-68 prostate-specific membrane antigen (⁶⁸ Ga-PSMA) PET/CT imaging revealed the second prostate primary cancer with evidence of bone metastases. Adoption of a dual PET/CT approach in cases where biopsy is impractical can achieve accurate staging results during the initial diagnostic workup.