Introduction: 131I-Metaiodobenzylguanidine (131I-MIBG) is used as palliative therapy in patients with metastatic neuroendocrine tumours (NET), but can cause bone marrow suppression, hypothyroidism and renal impairment.
Methods: Retrospective case note analysis identified 58 patients treated with between May 1996 and May 2006. We assessed the efficacy and toxicity of 131I-MIBG therapy in 49 of these patients (12men; mean age at diagnosis: 57.4 years; range 34 to 81) who had metastatic carcinoid tumours (31 gastroenteropancreatic, 6 pulmonary, 12 unknown origin) by identifying improvement in symptoms, radiographic changes, and changes in biochemical and haematological indices.
Results: 131I-MIBG was administered on 88 occasions to the 49 patients (mean 1.8 treatments, range 14). 36 patients (73.5%) responded to 131I-MIBG therapy with improvement in symptoms, radiology or biochemical indices. Symptomatic benefit was seen in 27patients (55.1%) post 131I-MIBG of whom 7 (14.3%) reported complete resolution of symptoms. Decreased tumour burden was evident on post therapy computer tomography (CT) and 123I-MIBG scans in 4 (8.2%) and 6 (12.2%) patients respectively. 23 patients (46.9%) were still alive at the time of the study. Of the 26 patients that had died, 18 had responded to treatment (50% of all responders) while 8 showed no response to treatment (61.5% of all non-responders). Median survival was 14.5 months (range 3 to 37 months) from completion of 131I-MIBG therapy in responders compared to 4 months (range 25 days to 72 months) in non-responders. 25 patients (51%) had adverse reactions of whom 1 died of sepsis within 30 days of treatment and 11 required hospitalisation. 10 developed thrombocytopaenia, 7 anaemia, 9 leucopaenia, 6 renal impairment and 3 abnormal thyroid function.
Conclusion: 131I-MIBG improved symptoms in the majority of patients with metastatic carcinoid tumours and patients that responded to treatment survived longer. Although, adverse events and hospitalisation were common, therapy related mortality was low.