CEA As a Diagnostic and Monitoring Biomarker in PSA-Negative Sarcomatoid Prostate Carcinoma: A Case Report

Prostatic sarcomatoid carcinoma (PSC) is a rare and aggressive form of prostate cancer. Its diagnosis is often complicated by the absence of prostate-specific antigen (PSA) expression, a key biomarker commonly used for prostate cancer detection and monitoring. Even more unusual is the elevation of carcinoembryonic antigen (CEA), a biomarker typically associated with gastrointestinal cancers, which can contribute to delayed diagnosis. We report the case of a 54-year-old man who presented with an isolated elevation in CEA (161 µg/L) during routine follow-up for ulcerative colitis. Initial gastrointestinal evaluations were unremarkable. Further urological assessment was conducted due to urinary complaints, revealing a prostate lesion despite normal PSA levels. Radical prostatectomy was subsequently performed, and final pathology identified a sarcomatoid carcinoma. Throughout follow-up, rising CEA levels consistently revealed multiple local recurrences and, eventually, lung metastases, whereas PSA remained within normal limits. Treatment with salvage radiotherapy, androgen deprivation therapy (ADT), and multiple chemotherapy regimens failed to control disease progression. A partial biochemical response was only achieved after the administration of carboplatin and cabazitaxel, with a significant decrease in CEA (from 303 to 158 µg/L) observed 54 months after diagnosis. This case highlights the diagnostic and therapeutic challenges associated with PSC, particularly in the setting of normal PSA and elevated CEA levels. It also underscores the potential utility of alternative biomarkers such as CEA in disease monitoring, and emphasizes the need for further research to establish effective treatment strategies for this rare and aggressive malignancy.