Investigation of Potential Splenic Metastasis on Prostate-Specific Membrane Antigen (PSMA) Imaging in High-Risk Prostate Cancer: A Role for MRI?

Computed tomography (CT), magnetic resonance imaging (MRI), and bone scintigraphy are utilized to diagnose and stage prostate cancer. There is a growing interest in the utilization of prostate-specific membrane antigen-positive emission tomography (PSMA PET) scans for the diagnosis and monitoring of prostate cancer. Here, we present a case of biopsy-proven prostate cancer with solitary focal splenic uptake on PSMA PET initially concerning for splenic metastasis. Further imaging with MRI indicated a benign splenic etiology in this case. The patient underwent radiation therapy (RT) and initiated two years of androgen deprivation therapy (ADT) for high-risk localized prostate adenocarcinoma. The patient's prostate-specific antigen (PSA) level decreased from a peak of 93.6 to 0.165 following treatment. Repeat PSMA PET scan three months post-radiation demonstrated no change in the splenic lesion despite decreased PSA. This case suggests that benign splenic lesions can demonstrate PSMA uptake on imaging and should be considered in cases of PSMA focal uptake in the spleen. This is significant because the presence of true metastases on PSMA PET scan significantly changes treatment recommendations for the patient. Further evaluation of benign findings that demonstrate PSMA avidity and appropriate follow-up testing for confirmation is necessary to avoid harmful overtreatment of patients.