Long-term outcomes of (131)Iodine mIBG therapy in metastatic gastrointestinal pancreatic neuroendocrine tumours: single administration predicts non-responders.

BACKGROUND: (131)Iodine (I131)-metaiodobenzylguanidine (mIBG) is a radionuclide-based treatment option for metastatic gastrointestinal-pancreatic neuroendocrine tumours (GEP NET). This study aimed at identifying prognostic indicators of long-term outcome based on initial evaluation following a first mIBG treatment (7400 MBq) in a patient cohort with such tumours, with a secondary aim of evaluating progression-free survival (PFS) and overall survival (OS) following mIBG therapy. METHODS: Retrospective review of the hospital records was performed to identify a cohort of 38 adult patients who underwent (131)Iodine-mIBG therapy over a 9-year period for metastatic GEP NETs and neuroendocrine tumours with an unknown primary. Treatment response was evaluated based on radiological criteria (RECIST1.1), biochemical markers [serum Chromogranin A (CgA)/urinary 5HIAA] and symptomatic response at clinical follow-up, all evaluated at 3-6 months from first mIBG treatment. Progression-free survival (PFS) and overall survival (OS) from the first mIBG treatment were recorded. RESULTS: At 3-6 months following a single mIBG therapy, 75%, 67%, and 63% of patients showed either a partial response (PR) or stable disease (SD) on radiological, biochemical, and symptomatic criteria, respectively. Complete response (CR) was not seen in any patient. OS from the date of diagnosis and from the first therapy was 8 years +/-1.1 (95% CI 5.7 to 10.2 years) and 4 years+/-0.69 (95% CI 2.6-5.3 years), respectively. Twenty-nine percent of patients were alive at 10 years. Significant survival advantage was seen in patients with SD/PR as compared to those who had progressive disease (PD) for each of these three criteria. CONCLUSION: Biochemical, radiological (RECIST 1.1) and symptomatic assessment of disease status at 3 to 6 months after first I131-mIBG therapy stratifies patients with a poor prognosis. This can be used to identify patients who may benefit from alternative strategies of treatment.

177Lu-Dotatate therapy for the treatment of metastatic neuroendocrine tumours in a patient on haemodialysis-dosimetric considerations.

We report on a case of a 68-year-old female, currently a dialysis-dependant patient with disseminated metastatic neuroendocrine tumour, treated with 177Lu-Dotatate. As 177Lu-Dotatate is cleared predominantly by the kidneys, there are concerns regarding the treatment plan strategy to avoid increased radiation exposure compared with patients with normal renal function. For this purpose, personalized dosimetry was used to calculate the safe administered activity using whole-body scans. Employing this strategy allowed us to adjust the administered activity for the third fraction. The whole-body doses calculated were not significantly different from those received by patients with normal renal function. The radiological follow-up showed a stable disease, suggesting effective treatment. We found negligible radiation protection problems involved with this procedure.