RESUMO
Peptide receptor radionuclide therapy (PRRT) is an effective therapeutic option in patients with metastatic neuroendocrine tumor (NET). However, PRRT fails in about 15-30% of cases. Identification of biomarkers predicting the response to PRRT is essential for treatment tailoring. We aimed to evaluate the predictive and prognostic role of semiquantitative and volumetric parameters obtained from the 68Ga-DOTATOC PET/CT before therapy (bPET) and after two cycles of PRRT (iPET). A total of 46 patients were included in this retrospective analysis. The primary tumor was 78% gastroenteropancreatic (GEP), 13% broncho-pulmonary and 9% of unknown origin. 35 patients (76.1%) with stable disease or partial response after PRRT were classified as responders and 11 (23.9%) as non-responders. Logistic regression analysis identified that baseline total volume (bTV) was associated with therapy outcome (OR 1.17; 95%CI 1.02-1.32; p = 0.02). No significant association with PRRT response was observed for other variables. High bTV was confirmed as the only variable independently associated with OS (HR 12.76, 95%CI 1.53-107, p = 0.01). In conclusion, high bTV is a negative predictor for PRRT response and is associated with worse OS rates. Early iPET during PRRT apparently does not provide information useful to change the management of NET patients.
RESUMO
Few data are available about radio-receptorial positron emission tomography (PET) results by the use of 68Ga-DOTA-peptides in pulmonary carcinoid tumours. In this study, we retrospectively analysed 68Ga-DOTATOC/PET and 18Fluorodeoxyglucose (FDG) PET diagnostic performances in 62 pulmonary carcinoids (occurring in 57 patients) and interrelationship with histological features. All patients underwent at least 1 PET/computed tomography: 26 patients received 68Ga-DOTATOC, 52 patients had 18F-FDG and 20 patients received both techniques. There were 55 typical carcinoids and 7 atypical carcinoids. 68Ga-DOTATOC/PET recorded an 88.4% overall detection rate (DR) (meanSUVmax: 15.5); 18F-FDG/PET a DR of 53.8% (meanSUVmax: 3.2). When adopted a maximum standardized uptake value-threshold of 1.5, DRs of 68Ga-DOTATOC and 18F-FDG/PET increased to 100% and 80.8%, respectively. Moreover, DRs in both techniques vary considerably according to histology with 68Ga-DOTATOC/PET having better performances in typical carcinoids than in atypical carcinoids (DR: 91.7% vs 50.0%, P = 0.076). We also observed a significant correlation between a low number of mitoses (<2/10 high-power field) and 68Ga-DOTATOC/PET-positivity (P = 0.004), and an association trend (P = 0.076) between necrosis and 68Ga-DOTATOC/PET-negativity. In conclusion, 68Ga-DOTATOC had better diagnostic performances than 18F-FDG/PET in detecting pulmonary carcinoids. DRs of both techniques remarkably varied according to histology with 68Ga-DOTATOC/PET performing at its best in typical carcinoids, whereas 18F-FDG/PET did the same in atypical carcinoids.68Ga-DOTATOC/PET results were presumably associated with the number of mitoses and the presence of necrosis.