Treatment Challenges in a Patient With Two Distinct Malignancies and Brain Metastases.

Prostate cancer (PC) is one of the leading causes of cancer death among men worldwide. Brain metastases from PC are very rare, often presenting in advanced stages of the disease, and are associated with a poor prognosis. Treatment is complex and may involve surgery or radiotherapy. We present the case of a 64-year-old male diagnosed with localized prostate adenocarcinoma, initially treated with pelvic radiotherapy associated with long-term hormonal treatment. While on this hormonal treatment, around one year after radical treatment initiation, he developed bilateral pulmonary metastases, histologically proven to be related to PC, defining a state of metastatic castration-resistant PC. He was asymptomatic and therefore treatment with enzalutamide was initiated. A partial response to the lung lesions was obtained and maintained for more than a year, at which time new mediastinal lymph node metastases were identified. An endobronchial ultrasound biopsy revealed metastases from carcinoma with neuroendocrine differentiation, favoring lung small-cell carcinoma. The patient started chemotherapy with carboplatin and etoposide, with a response. Due to the progression of the mediastinal lymph nodes after eight months, the patient had to undergo chemotherapy again, this time in combination with atezolizumab, with once again partial response. Given the possibility of drug interactions, enzalutamide was suspended during both cycles of chemotherapy and successfully reintroduced afterward. Three months after restarting enzalutamide, he began complaining of headaches. Brain imaging revealed a single frontobasal lesion, without evidence of simultaneous extracerebral progression. Considering the epileptogenic potential of enzalutamide, it was again suspended. The patient underwent surgery and histology revealed metastases of prostate adenocarcinoma, a very rare finding. Systemic re-staging after surgery revealed the progression of cerebral and extra-cerebral disease. The patient is currently proposed for treatment with whole brain radiotherapy and chemotherapy with docetaxel. This case demonstrates the difficulties associated with the diagnosis and treatment of a patient with two distinct neoplasms. Therapy choices were necessarily adjusted because of significant drug interactions. The diagnosis of brain lesions was the last complication, and it proved to be a challenge as it is a rare entity, with optimal management options not being well established.