RSNA: CT falls short in detecting neuroendocrine tumors in bone metastases

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CHICAGO--Though bone metastases in neuroendocrine tumors are usually sclerotic with increased bone volume, CT alone depicts only 43 percent of Ga-68-DOTATOC/DOTANOC-positive bone lesions, according to a retrospective analysis presented Nov. 29 at the Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).

With this study, Christian Krestan, MD, and colleagues from the Universitätsklinik für Radiodiagnostik Waehringer Guertel in Vienna, sought to evaluate the frequency and CT-morphology of 68-DOTATOC/DOTANOC PET/CT positive bone lesions in patients with histologically verified- neuroendocrine tumors. 

The researchers included a total number of 61 patients (mean age 57 years) with histologically proven-neuroendocrine tumors in this retrospective analysis. In all patients, they performed a 68Ga-DOTATOC PET/CT using a hybrid PET/CT scanner. The activity applied intravenously was between 150 MBq and 170 MBq Ga-68-DOTATOC/DOTANOC. All patients also underwent a spiral CT scan of the upper abdomen in the arterial phase, and a venous study from the skull to the symphysis.

In a consensus reading consisting of one radiologist and one nuclear medicine physician, the prevalence of Ga-68-DOTATOC /DOTANOC-positive bone lesions was analyzed. In addition, the researchers evaluated the CT morphology of these lesions using a bone window reconstruction.

In 11 percent of the patients, 68Ga-DOTATOC/DOTANOC-positive bone lesions were found in the ribs, pelvis, spine and temporal bone. In four patients, a single bone lesion was found and in three patients multiple lesions were found.

In 57 percent, the CT scan was negative, Krestan reported. In CT-positive bone lesions a slight sclerosis and increased bone volume was found. No osteolytic lesions were found. In the other 43 percent of patients, slight sclerosis and increased bone volume was found, whereas no osteolytic lesion could be detected. 

Thus, Krestan recommended the use of PET/CT, rather than CT in this patient population, due to the increased detection rate.