Specific efficacy of peptide receptor radionuclide therapy with (177)Lu-octreotate in advanced neuroendocrine tumours of the small intestine.

PURPOSE: Increasing evidence supports the value of peptide receptor radionuclide therapy (PRRT) in patients with metastatic neuroendocrine tumours (NET), but there are limited data on its specific efficacy in NET of small intestinal (midgut) origin. This study aims to define the benefit of PRRT with (177)Lu-octreotate for this circumscribed entity derived by a uniformly treated patient cohort. METHODS: A total of 61 consecutive patients with unresectable, advanced small intestinal NET G1-2 stage IV treated with (177)Lu-octreotate (4 intended cycles at 3-month intervals, mean activity per cycle 7.9 GBq) were analysed. Sufficient tumour uptake on baseline receptor imaging and either documented tumour progression (n = 46) or uncontrolled symptoms (n = 15) were prerequisites for treatment. Response was evaluated according to modified Southwest Oncology Group (SWOG) criteria and additionally with Response Criteria in Solid Tumors (RECIST) 1.1. Assessment of survival was performed using Kaplan-Meier curves and Cox proportional hazards model for uni- and multivariate analyses. Toxicity was assessed according to standardized follow-up laboratory work-up including blood counts, liver and renal function, supplemented with serial (99m)Tc-diethylenetriaminepentaacetic acid (DTPA) clearance measurements. RESULTS: The median follow-up period was 62 months. Reversible haematotoxicity (≥ grade 3) occurred in five patients (8.2%). No significant nephrotoxicity (≥ grade 3) was observed. Treatment response according to modified SWOG criteria consisted of partial response in 8 (13.1%), minor response in 19 (31.1%), stable disease in 29 (47.5%) and progressive disease in 5 (8.2%) patients. The disease control rate was 91.8%. Median progression-free survival (PFS) and overall survival (OS) was 33 [95% confidence interval (CI) 25-41] and 61 months (95% CI NA), respectively. Objective response was associated with longer survival (p = 0.005). Independent predictors of shorter PFS were functionality [hazard ratio (HR) 2.1, 95% CI 1.0-4.5, p = 0.05] and high plasma chromogranin A (CgA) levels > 600 ng/ml (HR 2.9, 95% CI 1.5-5.5, p < 0.001) at baseline. CONCLUSION: PRRT is well tolerated and very effective in advanced well-differentiated small intestinal (midgut) NET. A high disease control rate and long PFS can be achieved with this modality after failure of standard biotherapy with somatostatin analogues. Tumour functionality and high plasma CgA appear to be independent predictors of unfavourable patient outcome.

Early post-treatment FDG PET predicts survival after 90Y microsphere radioembolization in liver-dominant metastatic colorectal cancer.

PURPOSE: The aim of this study was to evaluate the predictive value of early metabolic response 4 weeks post-treatment using (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT in patients with unresectable hepatic metastases of colorectal cancer (CRC) undergoing radioembolization (RE) with (90)Y-labelled microspheres. METHODS: A total of 51 consecutive patients with liver-dominant metastases of CRC were treated with RE and underwent (18)F-FDG PET/CT at baseline and 4 weeks after RE. In each patient, three hepatic metastases with the highest maximum standardized uptake value (SUVmax) were selected as target lesions. Metabolic response was defined as >50 % reduction of tumour to liver ratios. Survival analyses using Kaplan-Meier and multivariate analyses were performed to identify prognostic factors for overall survival (OS). Investigated baseline characteristics included age (>60 years), performance status (Eastern Cooperative Oncology Group >1), bilirubin (>1.0 mg/dl), hepatic tumour burden (>25 %) and presence of extrahepatic disease. RESULTS: The median OS after RE was 7 months [95 % confidence interval (CI) 5-8]; early metabolic responders (n = 33) survived longer than non-responders (p < 0.001) with a median OS of 10 months (95 % CI 3-16) versus 4 months (95 % CI 2-6). Hepatic tumour burden also had significant impact on treatment outcome (p < 0.001) with a median OS of 5 months (95 % CI, 3-7) for patients with >25 % metastatic liver replacement vs 14 months (95 % CI 6-22) for the less advanced patients. Both factors (early metabolic response and low hepatic tumour burden) remained as independent predictors of improved survival on multivariate analysis. CONCLUSION: These are the first findings to show that molecular response assessment in CRC using (18)F-FDG PET/CT appears feasible as early as 4 weeks post-RE, allowing risk stratification and potentially facilitating early response-adapted treatment strategies.