Predictors of Survival in 211 Patients with Stage IV Pulmonary and Gastroenteropancreatic MIBG-Positive Neuroendocrine Tumors Treated with ¹³¹I-MIBG

Abstract

This retrospective analysis identifies predictors of survival in a cohort of patients with meta-iodobenzylguanidine (MIBG)-positive stage IV pulmonary and gastroenteropancreatic neuroendocrine tumor (P/GEP-NET) treated with ¹³¹I-MIBG therapy, to inform treatment selection and posttreatment monitoring. <b>Methods:</b> Survival, symptoms, imaging, and biochemical response were extracted via chart review from 211 P/GEP-NET patients treated with ¹³¹I-MIBG between 1991 and 2014. For patients with CT follow-up (<i>n</i> = 125), imaging response was assessed by RECIST 1.1 if images were available (<i>n</i> = 76) or by chart review of the radiology report if images could not be reviewed (<i>n</i> = 49). Kaplan-Meier analysis and Cox multivariate regression estimated survival and progression-free survival benefits predicted by initial imaging, biochemical response, and symptomatic response. <b>Results:</b> All patients had stage IV disease at the time of treatment. Median survival was 29 mo from the time of treatment. Symptomatic response was seen in 71% of patients, with the median duration of symptomatic relief being 12 mo. Symptomatic response at the first follow-up predicted a survival benefit of 30 mo (<i>P</i> < 0.001). Biochemical response at the first clinical follow-up was seen in 34% of patients, with stability of laboratory values in 48%; response/stability versus progression extended survival by 40 mo (<i>P</i> < 0.03). Imaging response (20% of patients) or stability (60%) at the initial 3-mo follow-up imaging extended survival by 32 mo (<i>P</i> < 0.001). Additionally, multiple ¹³¹I-MIBG treatments were associated with 24 mo of additional survival (<i>P</i> < 0.05). <b>Conclusion:</b> Therapeutic ¹³¹I-MIBG for metastatic P/GEP-NETs appears to be an effective means of symptom palliation. Imaging, biochemical, and symptomatic follow-up help prognosticate expected survival after ¹³¹I-MIBG therapy. Multiple rounds of ¹³¹I-MIBG are associated with prolonged survival.