Abstract
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Objectives Increasing evidence supports the efficacy of peptide receptor radionuclide therapy (PRRT) in patients with metastatic NET, but there is limited data regarding the particular efficacy in NET of small intestinal (midgut) origin. We evaluated the outcome of PRRT with 177Lu-octreootate in a uniformly treated patient cohort of metastatic midgut NET G1-2.
Methods 70 patients with inoperable metastatic disease treated with 177Lu-octreotate (4 intended cycles at 3 monthly intervals; mean activity per cycle, 8.0 GBq). Response was evaluated according to modified Southwest Oncology Group (SWOG). Survival analyses were performed using Kaplan-Meier curves and Cox proportional hazards model for uni- and multivariate analyses. Toxicity was assessed according to standardized follow-up lab work-up including blood counts, liver and renal function measurements.
Results The mean follow-up period was 57 months. Reversible hematotoxicity (≥ grade 3) occurred in 5 patients (7.1%). No significant nephrotoxicity (≥ grade 3) was observed. Treatment response consisted of partial response in 9 (12.9%), minor response in 14 (20%), stable disease in 40 (57.1%), and progressive disease in 7 (10%) patients. The disease control rate was 90%. Median progression-free survival (PFS) and overall survival (OS) were 31 (95% CI, 25-37) and 58 months (95% CI, 45-71), respectively. Predictors of survival were a positive responder status (OS, p=0.003), G1 grading (PFS, p=0.013; OS, p=0.045), and a CgA level < 600 ng/ml (PFS, p= 0.001; OS, 0.045).
Conclusions PRRT is very effective in well-differentiated midgut NET with a high disease control rate (90%) and long progression-free survival (median 31 mo). Independent predictors of long-term outcome are the Ki67-based tumor grading and plasma CgA level.