Endocrine Abstracts

Introduction: Choline PET-CT is a recognised modality for imaging prostate cancer; both for initial staging and restaging. It is, however, a non specific tracer and is also positive in numerous other conditions such as inflammatory processes and other malignancies.

Method: We present a case of a 60 year old patient with a PSA of 9 ng/ml and a firm abnormal right prostate lobe. Prostate MRI demonstrated a lesion in the apex of the prostate but no associated lymphadenopathy. The isotope bone scan was negative. As the patient was considered high risk for malignancy and in view of his rising PSA, an 18F choline PET-CT was performed to exclude nodal and distant metastatic disease.

Results: The choline PET-CT scan showed increased uptake at the apex of the right prostate gland corresponding to the tumour identified on pelvic MRI. In addition, there was increased uptake in a conglomerate mass of mesenteric lymph nodes to the right of the midline at the level of L₃/L₄. There was associated calcification and mesenteric stranding. Further foci of relatively reduced uptake were also seen in the liver. A subsequent contrast enhanced CT confirmed the enhancing mesenteric mass lesion and the hepatic lesions in segment VIII. These lesions also demonstrated increased uptake on an Indium Octreotide SPECT CT imaging. This lesion was confirmed to represent well differentiated NET and the patient was commenced on lanreotide treatment.

Discussion: Malignancies including prostate cancer express choline transport and choline kinase enzymes. Choline PET-CT is useful for the staging prostate cancer when conventional imaging is inconclusive/ equivocal or there is undiagnosed spread in high risk cases. It has a sensitivity of 66–81% and specificity 43–87% in prostate cancer. However, as demonstrated it can also be positive in other malignancies including NET and other inflammatory conditions.

Conclusion: Choline PET-CT is not used as a primary diagnostic or staging procedure for NET but it can be diagnosed incidentally on such studies. The CT appearance and location of NET are well recognised with subsequent somatostatin receptor imaging, biopsy and biochemical markers confirming the diagnosis.