Onkológia 4/2020

PET findings in rare prostate cancers – neuroendocrine prostate cancer – case report

Purpose: Rare types of prostate cancer pose a diagnostic challenge. These include neuroendocrine types of prostate cancer (NEPC) expressing somatostatin receptors, which are a suitable target for diagnostics using somatostatin analogs. This type of examination is PET/CT with 68Ga-DOTA peptides, which in this uncommon indication can significantly contribute to the improvement of the management of a patient with this rare type of prostate tumor. Case: In a 73-year-old patient diagnosed with prostate cancer, a radical retropubic prostatectomy was performed after a previous diagnostic biopsy, with a histological finding of acinar prostate adenocarcinoma Gleason score 7 (4 + 3), Grade Group 3. Over time, PSA values progressed. MRI found recurrence, which was subsequently surgically removed, histologically with the finding of transformation into a neuroendocrine prostate tumor. External radiotherapy was added for ongoing hormonal treatment. Gradually, during the development of the disease, repeated PET/ CT examinations with 68Ga-PSMA were performed, where the expression of PSMA receptors on prostate cancer cells decreases or disappears, due to dedifferentiation and transformation into a neuroendocrine type of tumor. In order to assess the extent of the disease when the histological type of the tumor changed, PET/CT examinations with 68Ga-DOTA-TOC and 18FDG were performed, with extensive positive findings on both. Conclusion: The neuroendocrine type of prostate tumor can, in very rare cases, occur as the primary type. More often, however, the already known prostate adenocarcinoma, or its metastases, is transformed into a neuroendocrine type of tumor, or it is dedifferentiated, gradually during treatment. Such a change in the histological type of the tumor can be diagnosed through biopsy and the stage of the disease by targeted PET/CT examinations with radiopharmaceuticals focused on the expression of somatostatin receptors, or on glucose metabolism of dedifferentiated tissue. Based on the results of these examinations, consideration is given to the eventual possibility of using somatostatin analogues in the treatment of this type of prostate cancer, or the use of radionuclide treatment.

Keywords: PET/CT, 68Ga-PSMA, 68Ga-DOTA, NEPC, prostate cancer