PSMA/PET-guided stereotactic radiosurgery treatment for intracranial metastases from prostate cancer

Purpose: Prostate-specific membrane antigen-targeted molecular imaging with positron emission tomography (PSMA/PET) is being increasingly incorporated into the clinical care of patients with suspected metastatic or biochemically recurrent prostate cancer, allowing for metastasis-directed therapies. Brain metastases from prostate cancer are rare and portend a poor prognosis. We present a case series of patients with intracranial prostatic brain metastasis detected on PSMA/PET and discuss its application for cranial radiosurgery. Methods: A prospectively collected database was queried for prostate cancer patients who presented with intracranial metastasis based on PSMA/PET from January 2020 to December 2024 in a single institution. The clinical course, imaging findings, and treatments were reviewed. Results: Among the prostate cancer patients treated at the Gamma Knife radiosurgery (GKRS) department, ten had undergone PSMA/PET after biochemical recurrence, yielding a new diagnosis of single or multiple intracranial metastases, with brain, calvarial, or dural lesions (mean standardized uptake value of 12.5). Their median age was 64 years. Two patients presented with headaches and two suffered from neurologic changes. The prescribed dose ranged from 12 to 21 Gy in one to three fractions. Brain MRI was acquired for all patients and showed that lesions up to 0.061 cc presented a false negative result. Patients were monitored for a median of 6.5 months with brain MRIs, only two with PSMA/PET. Four patients underwent GKRS in addition to treatment with 177Lu-PSMA, with no evidence of acute radiation toxicity. Conclusions: Brain metastases from prostate cancer are rare and can be effectively treated with GKRS. PSMA/PET combined with MRI allows for improved detection of new or recurrent brain metastases and treatment response evaluation.