Widespread Metastases in Small Cell Carcinoma of the Prostate on FDG PET/CT

Mismatched Lesions on 18F-FDG PET and 18F-Fluciclovine PET Images in a Patient With Metastatic Prostate Small Cell Carcinoma

ABSTRACT

A 65-year-old man with fluciclovine-avid metastatic prostate small cell carcinoma with prostate-specific antigen (PSA) 19.4 ng/mL at diagnosis underwent system therapy and subsequent surgery and achieved hormonal response with PSA <0.1 ng/mL. An 18F-fluciclovine PET/CT scan 3 months after surgery was negative for disease. Although PSA remained <0.1 ng/mL, the rising carcinoembryonic antigen prompted an 18F-FDG PET/CT 6 weeks later. It showed multiple hypermetabolic lesions in the prostatectomy bed, liver, and right iliac bone, suggestive of malignant disease. The FDG-avid prostatectomy lesions were further confirmed on MRI. This case demonstrates that FDG PET/CT has a role in suspected metastatic prostate small cell carcinoma with negative fluciclovine PET examination.

Neuroendocrine neoplasms of the genitourinary tract in adults: cross-sectional imaging spectrum

Neuroendocrine (NE) neoplasms of the genitourinary (GU) tract in adults are rare tumors with distinct histopathology and variable biological behavior and imaging findings. They may be primary or metastatic in origin. The spectrum of primary GU tract NE neoplasms includes carcinoid, small cell carcinoma, large cell NE carcinoma, and paraganglioma. The tumors commonly show positivity to specific immunohistochemical markers and characteristic dense-core granules at the ultra-structural level. Although imaging findings are nonspecific and accurate differentiation from the more common malignancies of the individual organs is not possible, cross-sectional imaging modalities play an important role in the diagnosis, staging, and surveillance of these tumors. Somatostatin receptor scintigraphy (octreotide scan) may be useful in the detection and treatment of metastatic disease in select patients. Knowledge of the various NE tumors of the adult GU tract and familiarity with their pathological and imaging findings permit optimal patient management.

18F-fluorodihydroxyphenylalanine vs other radiopharmaceuticals for imaging neuroendocrine tumours according to their type

6-Fluoro-(¹⁸F)-L-3,4-dihydroxyphenylalanine (FDOPA) is an amino acid analogue for positron emission tomography (PET) imaging which has been registered since 2006 in several European Union (EU) countries and by several pharmaceutical firms. Neuroendocrine tumour (NET) imaging is part of its registered indications. NET functional imaging is a very competitive niche, competitors of FDOPA being two well-established radiopharmaceuticals for scintigraphy, ¹²³I-metaiodobenzylguanidine (MIBG) and ¹¹¹In-pentetreotide, and even more radiopharmaceuticals for PET, including fluorodeoxyglucose (FDG) and somatostatin analogues. Nevertheless, there is no universal single photon emission computed tomography (SPECT) or PET tracer for NET imaging, at least for the moment. FDOPA, as the other PET tracers, is superior in diagnostic performance in a limited number of precise NET types which are currently medullary thyroid cancer, catecholamine-producing tumours with a low aggressiveness and well-differentiated carcinoid tumours of the midgut, and in cases of congenital hyperinsulinism. This article reports on diagnostic performance and impact on management of FDOPA according to the NET type, emphasising the results of comparative studies with other radiopharmaceuticals. By pooling the results of the published studies with a defined standard of truth, patient-based sensitivity to detect recurrent medullary thyroid cancer was 70 % [95 % confidence interval (CI) 62.1–77.6] for FDOPA vs 44 % (95 % CI 35–53.4) for FDG; patient-based sensitivity to detect phaeochromocytoma/paraganglioma was 94 % (95 % CI 91.4–97.1) for FDOPA vs 69 % (95 % CI 60.2–77.1) for ¹²³I-MIBG; and patient-based sensitivity to detect midgut NET was 89 % (95 % CI 80.3–95.3) for FDOPA vs 80 % (95 % CI 69.2–88.4) for somatostatin receptor scintigraphy with a larger gap in lesion-based sensitivity (97 vs 49 %). Previously unpublished FDOPA results from our team are reported in some rare NET, such as small cell prostate cancer, or in emerging indications, such as metastatic NET of unknown primary (CUP-NET) or adrenocorticotropic hormone (ACTH) ectopic production. An evidence-based strategy in NET functional imaging is as yet affected by a low number of comparative studies. Then the suggested diagnostic trees, being a consequence of the analysis of present data, could be modified, for some indications, by a wider experience mainly involving face-to-face studies comparing FDOPA and ⁶⁸Ga-labelled peptides.

Clinical impact of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in the evaluation of small cell carcinoma of the prostate

Small cell carcinoma of prostate (PSCC) is an uncommon and aggressive type of prostate malignancy with limited data on the use of (18)F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) in the clinical management of this rare entity. In this report, clinical and imaging findings of a patient with PSCC are presented. We aimed to discuss the role of PET/CT in the evaluation of PSCC in combination with histopathological characteristics of tumor and emphasize the importance of PET/CT in the clinical management of PSCC.