This study aimed to assess the clinical impact of 68 Ga-DOTATATE and 18 F-FDG with respect to the management plan and to evaluate the prognostic value of both tracers. Methods: A total of 104 patients (55 male and 49 female; median age, 58 y; range, 20-90 y) with histologically proven neuroendocrine tumors (NETs) underwent both 68 Ga-DOTATATE and 18 F-FDG PET/CT. . Results: The 68 Ga-DOTATATE and 18 F-FDG PET/CT findings were discordant in 65 patients (62.5%) and concordant in 39 patients (37.5%). The results changed the therapeutic plan in 84 patients (80.8%). In 22 patients (21.1%), decision making was based on the 18 F-FDG findings; in 32 (30.8%), on the findings with both radiotracers; and in 50 (48.1%), on the 68 Ga-DOTATATE findings. The most frequent management decision based on 18 F-FDG was initiation of chemotherapy (10 patients, 47.6%). The most common treatment decision due to 68 Ga-DOTATATE was initiation of peptide receptor radionuclide therapy (14 patients, 27.4%). In 11 (39.2%) of 28 patients with poorly differentiated NETs, the management decision was based on only the 18 F-FDG results. For 68 Ga-DOTATATE, SUV max was higher for G1 tumors and lower for G3 tumors (P 5 0.012). However, no significant differences in 18 F-FDGderived SUVs were observed between different grades (P 5 0.38). The Mann-Whitney test showed significant differences in 68 Ga-DOTATATE SUV max between tumors with a Ki-67 of less than 5% and tumors with a Ki-67 of more than 5% (P 5 0.004), without significance differences in 18 F-FDG SUV max . Log-rank analysis showed statistically significant differences in survival for patients with bone metastasis versus soft-tissue or no metastasis for both 18 F-FDG (P 5 0.037) and 68 Ga-DOTATATE (P 5 0.047). Overall survival declined rapidly with increasing grade (P 5 0.001), at an estimated 91 mo for G1, 59 mo for G2, and 48 mo for G3. Conclusion: 18 F-FDG PET/CT had no clinical impact on G1 NETs and a moderate impact on G2 NETs. However, in poorly differentiated NETs, 18 F-FDG PET/CT plays a significant clinical role in combination with 68 Ga-DOTATATE. 68 Ga DOTATATE SUV max relates to grade and Ki-67 and can be used prognostically.

Background:The antiproliferative activity of octreotide LAR in neuroendocrine tumours (NETs) has been demonstrated by small retrospective studies and confirmed by a prospective phase III trial (PROMID). However, there are limited data about the duration and predictors of response. The aim of our retrospective study was to determine the time to radiological progression (TTRP) of disease and the factors that were associated with better response.Methods:A total of 254 treatment naïve patients with advanced NETs and positive somatostatin receptor scintigraphy were included. Mean follow-up period was 42 months.Results:The location of primary was in the small bowel in 204, pancreas in 22, lungs in 14, rectum in 7 and unknown in 7 patients. Most tumours were well-differentiated, G1 (58%) and G2 (23%). The majority of patients commenced octreotide LAR due to functional symptoms (57%), radiological progression (10%) or in the presence of asymptomatic and stable disease on the basis of data from the PROMID trial (18.5%). Partial response occurred in 5%. For all patients, the median TTRP was 37 months (95% confidence interval, CI: 32–52 months). There was a statistically significant shorter TTRP in patients with pancreatic tumours, liver metastases and intermediate grade tumours. Extremely raised (>10 times the upper limit of normal) baseline chromogranin A levels were associated with an unfavourable outcome. In contrast, male sex, carcinoid heart disease and initiation of treatment in the presence of stable disease were predictive of a better response. Age, extra-hepatic metastases, presence of mesenteric desmoplasia, previous resection and functional status of the primary tumour did not affect response.Conclusions:The duration of the antiproliferative effect of octreotide LAR seems to be longer than previously reported. This study has identified several predictors of response in a large cohort of patients with NETs on somatostatin analogue therapy.

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