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

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 I-MIBG therapy, to inform treatment selection and posttreatment monitoring. Survival, symptoms, imaging, and biochemical response were extracted via chart review from 211 P/GEP-NET patients treated with I-MIBG between 1991 and 2014. For patients with CT follow-up ( = 125), imaging response was assessed by RECIST 1.1 if images were available ( = 76) or by chart review of the radiology report if images could not be reviewed ( = 49). Kaplan-Meier analysis and Cox multivariate regression estimated survival and progression-free survival benefits predicted by initial imaging, biochemical response, and symptomatic response. 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 ( < 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 ( < 0.03). Imaging response (20% of patients) or stability (60%) at the initial 3-mo follow-up imaging extended survival by 32 mo ( < 0.001). Additionally, multiple I-MIBG treatments were associated with 24 mo of additional survival ( < 0.05). Therapeutic I-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 I-MIBG therapy. Multiple rounds of I-MIBG are associated with prolonged survival.