Aims: Neuroendocrine neoplasms are a heterogeneous group of tumours which are increasing in incidence. Appendiceal NENs are often incidentally detected, are generally benign and carry a low risk of recurrence. (Singh 2018) [68Ga]-DOTATATE PET is known to be more sensitive than cross-sectional imaging, and is increasingly used in postoperative imaging to ensure there is no residual disease. We hypothesize that these scans have a low likelihood of showing residual disease in patients with low-risk appendiceal NENs (appNENs).
Methods: Retrospective study of all patients who underwent [68Ga]-DOTATATE PET at Royal North Shore Hospital 0-18 months after resection of appendiceal NEN. Scans were reviewed independently of original report by an experienced nuclear medicine physician. The primary outcome was the proportion of patients whose scans demonstrated PET uptake to suggest residual disease.
Results: From 2011 to 2014 25 consecutive patients were identified in the pilot phase of the study. The median age was 32 (range 17-74) and 64% were female. The median time after surgery was 4.3 months (range 0.3-17.6). All patients underwent appendiceal resection and three subsequently underwent hemicolectomy due to high-risk pathology. Pathology was as follows: Size - median 9mm (range 1-32). Location – distal 73%, middle 20%, proximal 7%. All tumours were well-differentiated and Grade 1 where graded by WHO 2010. No scans showed definitive residual or distant disease. 3/25 scans showed abnormalities requiring follow-up – one unrelated to neuroendocrine pathology (thyroid uptake) and two indeterminate (bowel loop, vertebral lesion).
Conclusions: Post-operative use of [68Ga]-DOTATATE PET did not detect any residual or distant disease after resection of appNENs. Despite its superior sensitivity compared to cross-sectional imaging, it is not recommended as part of staging after completely resected localized appNENs.