Orbital and brain metastases on 68Ga-PSMA PET/CT in a patient with prostate carcinoma refractory to 177Lu-PSMA and 225Ac-PSMA therapy

Abstract

We present a case of metastatic prostate cancer with rare metastases involving the brain and orbit, in addition to liver, skeletal and nodal metastases. The patient had undergone prior hormonal therapy and chemotherapy and had disease progression despite 2 cycles of ¹⁷⁷Lu-Prostate specific membrane antigen (¹⁷⁷Lu-PSMA) based radioligand therapy. He had a partial response after 2 cycles of ²²⁵Ac-PSMA based targeted alpha therapy, as demonstrated on the ⁶⁸Ga-PSMA PET/CT study. However, the patient had disease progression at the end of 4 cycles of ²²⁵Ac-PSMA therapy, evident by rising prostate specific antigen levels and imaging findings. The end of treatment ⁶⁸Ga-PSMA PET/CT showed additional sites of metastases in the orbit and brain apart from overall disease progression. These are rare sites of distant spread in prostate cancer and require urgent evaluation and local treatment to prevent potential complications. The importance of detection of metastatic sites in closed cavities is because of the requirement for urgent intervention to avoid compression related complications.

Keywords: CNS; Ocular; PET/CT; Prostate Specific Membrane Antigen; Prostate cancer.