Adenoid cystic carcinoma of the prostate: an unusual subtype of prostate cancer

Abstract

Adenoid cystic carcinoma (ACC) of the prostate is an extremely rare disease that arises from the basal cells of prostate acini and presents a poor prognosis for metastatic cases. Multiple treatment options exist for different stages of prostate cancer that include prostatectomy, radiation therapy, chemotherapy, and hormone therapy with gonadrotropin-releasing hormone (GnRH) agonists and antagonists for androgen receptor (AR)-positive cases. Although ACC has a biological potential that allows metastasis in a few cases; the current treatment option consists primarily of surgical resection along with close, long-term follow-up. Herein, we report this rare entity in a 79-year-old man who presented with liver metastasis. The tumor expressed GnRH receptor (GnRHR) and a very low level of Programmed death-ligand 1 (PD-L1). Immunohistochemical analysis revealed that the primary tumor was highly proliferative and AR-negative. We employed a clinically validated technology that utilizes patient’s tumor and blood to recreate the tumor microenvironment ex vivo. After the diagnosis, we used the platform to test the efficacy of degarelix (a GnRHR antagonist), atezolizumab (a PD-L1 antagonist) and paclitaxel + carboplatin chemotherapeutic regimen. The assay output predicted response with chemotherapeutics and degarelix, without any sign of efficacy for PD-L1 antagonist. On the basis of these data, the patient was treated with paclitaxel + carboplatin combination chemotherapy first and showed clinical and radiological response as predicted by the ex vivo platform. After 4 cycles of chemotherapy, the patient received maintenance therapy with degarelix and demonstrated a favorable clinical response. Taken together, our results not only showed the accurate prediction of clinical outcome but also demonstrate the rational selection of a regimen as a viable option for such a clinically challenging disease.

Keywords

Adenoid cystic carcinoma / prostate cancer / chemotherapy / degarelix

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