Clinical challenge: Cystic brain metastasis from prostate ca
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Prostate carcinoma is the most common malignancy among men in Western countries. Although this cancer can metastasize to any organ, metastatic invasion of the central nervous system is very rare. Indeed, from 0.3 to 2.8% of patients with prostate cancer will be affected by such a condition. There appears to be an increase in the incidence of brain metastases from prostate cancer over the past two decades that may reflect the gain in survival. Though cystic brain metastases are still very rare and only a few cases have been reported in the literature. Here we present an unusual case of a large polycystic brain metastasis from prostate cancer.

A 71-year-old male was diagnosed with high risk localized prostate adenocarcinoma given that the Gleason score was 10 (5 + 5) on biopsy. Gonadorelin analogous decapeptide hormone therapy was started and he received prostatic radiotherapy of 8,000 cGy (cGy) in 40 fractions combined with prophylactic irradiation of the pelvic lymph nodes of 5,600 cGy in 23 fractions. Within a year, it relapsed in the form of lymph nodes involvement, lung tumor, and multiple bone lesions despite chemical castration.

He underwent first-line docetaxel chemotherapy followed by a second line of cabazitaxel with spinal radiotherapy due to bone progression in the axial skeleton resulting in epidural compressions. Afterward, he receives a third line of enzalutamide chemotherapy due to poor tolerance of cabazitaxel. At that time, his overall tumor lesions and PSA levels remained stable. The patient was then admitted for repeated falls. His clinical examination revealed no neurological impairment. A magnetic resonance imaging (MRI) of his brain showed a 27 mm polycystic lesion in the left parietal region without peripheral edema.

MR spectroscopy with relative cerebral blood volume measurement was performed showing marked hyperperfusion and tumor-like biochemical profile within this cystic lesion and finding out three others suspicious-looking intraparenchymal lesions (left temporal, right occipital and left frontal areas) measuring 6 mm, 6 mm and 4 mm respectively.
The metastatic nature of these brain lesions was therefore retained. As the patient began to develop symptoms such as hemiparesis and headache, he received whole-brain radiation therapy at a dose of 3,000 cGy in 10 fractions. He was still alive 4 months after the RMI diagnosis of brain metastases.