Small Cell Transformation of Metachronous ALK + ve Lung and Prostatic Adenocarcinoma following Initial Response to Ceritinib and Androgen Deprivation Therapies and Metastases to Two Different Organs: Guidance through FDG-PET/CT and 68 Ga-PSMA-11 PET-CT and Biopsy-Immunohistochemistry Correlation.

Metachronous malignancies carry poor prognosis and pose certain challenges for management of two different malignancies simultaneously. A 59-year-old male, a patient of ALK+ lung adenocarcinoma demonstrating excellent initial response to targeted therapy with ALK inhibitor ceritinib, developed prostatic adenocarcinoma with neuroendocrine differentiation 36 months later, which was treated with abiraterone and leuprolide. Dual-tracer positron emission tomography (PET) imaging with 18 F-FDG-PET/computed tomography (CT) and 68 Ga-PSMA-11 PET/CT showed complete response of prostatic adenocarcinoma with controlled serum prostate-specific antigen level, showed new-onset metastatic brain and liver lesions 12 months later, the biopsy of the later revealed metastatic small cell neoplasia. The clinical profile, dual tracer PET/CT and immunohistochemistry correlation assisted in concluding that prostate adenocarcinoma had transformed into small cell type, which metastasized to liver, whereas the lung adenocarcinoma had metastasized to brain.