Postoperative Ga-DOTATATE positron emission tomography has a low yield in incidental appendiceal neuroendocrine tumours.

INTRODUCTION

Rarely, appendiceal neuroendocrine tumours (NET) are an incidental finding when an appendicectomy is undertaken for suspected appendicitis. The role of further imaging in this setting is poorly defined. Positron emission tomography (PET) using Ga-DOTATATE is requested to evaluate post-surgical status, however, there is little evidence to guide how it should be employed. The aims of this project are to: (i) characterize Ga-DOTATATE PET findings in patients with incidental appendiceal NETs and (ii) discuss how these data might inform post-surgical imaging with PET.

METHODS

We reviewed 47 PET scans in 30 patients, undertaken from 2009 to 2018. Scintigraphic findings, histopathological characteristics of the initial appendiceal lesion and medical records were reviewed.

RESULTS

Most patients (n = 15) had small (<10 mm) appendiceal NETs with low grade (Ki67 < 2%) features. Eight patients had tumours between 10 and 20 mm, and seven had tumours >20 mm. Goblet cell features were identified in two patients. Three positive PET scans were reported in one patient with an index tumour measuring 40 mm and Ki67 < 2%. The remaining 29 patients had 44 negative scans. Clinical outcome data were available in 27 patients (mean follow-up time 57 months; range 6-123 months). There was no evidence of recurrent neuroendocrine disease at the time of the last follow-up.

CONCLUSION

These data indicate that in most cases, post-surgical Ga-DOTATATE PET is negative in patients with incidentally detected appendiceal NETs. Clinical outcome data suggest that Ga-DOTATATE PET should be reserved for patients with large tumours (>20 mm) or those displaying goblet cell features.