Yuji Nakamoto MD, PhD, Presenter: Nothing to Disclose

Kohei Sano PhD, Abstract Co-Author: Nothing to Disclose

Takayoshi Ishimori MD, PhD, Abstract Co-Author: Nothing to Disclose

Maya Kato Arimoto MD, Abstract Co-Author: Nothing to Disclose

Tomomi Nobashi, Abstract Co-Author: Nothing to Disclose

Kaori Togashi MD, PhD, Abstract Co-Author: Research Grant, Bayer AG Research Grant, DAIICHI SANKYO Group Research Grant, Eisai Co, Ltd Research Grant, FUJIFILM Holdings Corporation Research Grant, Nihon Medi-Physics Co, Ltd Research Grant, Shimadzu Corporation Research Grant, Toshiba Corporation Research Grant, Covidien AG

PET/CT with 68Ga-DOTATOC has been used for detection of neuroendocrine tumors, but the optimal duration after administration of DOTATOC has not been fully investigated. The purpose of this study was to investigate whether delayed scanning at about 90-min post-injection had any clinical benefits for evaluating neuroendocrine tumors, comparing with conventional scanning at 60-min post-injection.

57 patients (M:F=25:32, mean 55 yr) who underwent DOTATOC-PET/CT scan for suspected or known neuroendocrine tumors were retrospectively evaluated. PET/CT scanning was performed twice at about 1-h and 1.5-h post-injection. For visual analysis, a 5-point grading scale (0: definitely normal – 4: definitely abnormal) was used, and lesions with grade 3 or 4 were regarded as positive. For quantitative analysis, standardized uptake values for each lesion and physiological uptake in liver were evaluated. When patients had more than five lesions (SUVs), representative 5 lesions were assessed.

Of 57 patients, 44 patients had a total of 133 lesions (83 in liver, 20 in pancreas, 10 in bone, 10 in lymph node, and 10 in others), and 13 patients were negative. In interpreting early images, there were 3 lesions with grade 3, but the remaining 130 lesions were grade 4. All 133 lesions were grade 4 in delayed images, and there were no lesions which were suspected in either scanning. The physiological uptake in liver was comparable between the two scanning (Mean±SD=5.6±1.8). SUVs and tumor-to-liver ratios of hepatic lesions were slightly higher in early scanning than in delayed scanning (SUV; 26.5±20.7 : 28.0±20.8, Tumor-to-liver ratio; 6.0±4.4 : 6.4±4.5, p<0.01), which did not affect detectability. In addition, bone and peritoneal metastases had slightly higher SUVs at delayed images as well (p<0.05), without difference of diagnostic performance. There was no significant difference in SUVs of pancreatic lesions and primary sites of midgut between the two scans.

Our preliminary data suggest that the delayed scan had no specific merits for detecting primary or metastatic neuroendocrine tumors, although it could be helpful for improving diagnostic confidence.

In DOTATOC-PET/CT, the delayed scanning at 90-min postinjection had no specific merits for detecting neuroendocrine tumors, as compared with conventional scanning at 60-min postinjection, although diagnostic confidence may be changed.

Nakamoto, Y, Sano, K, Ishimori, T, Arimoto, M, Nobashi, T, Togashi, K, Clinical Efficacy of Delayed Scanning of 68Ga-DOTATOC-PET/CT in Detecting Neuroendocrine Tumors.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14009014.html