The Impact of Radiological Response to Peptide Receptor Radionuclide Therapy on Overall Survival in Patients With Metastatic Midgut Neuroendocrine Tumors.

PURPOSE OF THE REPORT: Peptide receptor radionuclide therapy (PRRT) is an effective treatment for advanced neuroendocrine tumors (NET); however, long-term survival data are scarce. The aim of this study is to determine long-term survival in patients with metastatic midgut NET, according to response to PRRT.

PATIENTS AND METHODS: One hundred thirty-three consecutive patients with progressive metastatic midgut NET underwent PRRT. Response at 1 year post PRRT was classified as partial response, stable disease, disease progression, or death. Survival was assessed according to response to PRRT, and predictors of overall survival (OS) and progression-free survival (PFS) were identified.

RESULTS: At 1 year post PRRT, 9% had partial response, 50.4% stable disease, 10.5% disease progression, and 30.1% were dead. The OS was 33.5, and PFS was 28.5 months. Predictors of disease progression/death were chromogranin A greater than 10 ULN (OR, 4.6; P = 0.007) and hepatic tumor load greater than 50% (OR, 5; P = 0.004). There was no difference in OS between patients with partial response and those with stable disease post PRRT. In multivariate Cox regression, predictors of OS were number of PRRT cycles (HR, 0.33; P < 0.0005), hepatic tumor load greater than 50% (HR, 3.46; P = 0.01), and outcome at 1 year post PRRT (HR, 21.37; P < 0.0005). Predictors of PFS were number of PRRT cycles (HR, 0.39; P < 0.0005), previous resection of liver metastases (HR, 3.56; P = 0,023), and hepatic tumor load greater than 50% (HR, 3.06; P < 0.0005).

CONCLUSIONS: Patients with progressive metastatic midgut NET who achieved stable disease at 1 year post PRRT had similar OS with those with partial response. Hepatic tumor burden was a strong predictor of response to PRRT, PFS, and OS.