Endocrine Abstracts

Background: Appendiceal neuroendocrine tumours (aNETs) are usually diagnosed incidentally at appendicectomy, are indolent and rarely recur. Current ENETS guidelines inform aNETs management and highlight areas of uncertainty. We aimed to identify risk factors that predict lymph node metastasis, residual disease at completion surgery, or disease recurrence and also assessed survival according to ENETS stage.

Methods: We retrospectively analysed a prospective database of patients diagnosed at our centre with aNETs from 1990 to 2016. We assessed risk factors for nodal metastases detected at primary or completion surgery, for residual disease at completion surgery, or for disease recurrence using logistic regression models. We assessed overall and aNET-specific survival using Kaplan-Meier analysis.

Results: 93 patients (39 males, 54 females, median 47.9 (range 16.3–78.8) years) were included. Unsurprisingly, lymph node metastases significantly (P=0.0015) correlated with tumour size >2.0 cm. Residual disease was significantly predicted by tumour grade ≥G2 (P=0.0418) and goblet cell carcinoma (GCC) histology (P=0.0390). Disease recurrence was significantly predicted by GCC histology (P=0.0002). In the only recurrence where the primary aNET was non-GCC, the patient had undergone R1 resection of an ENETS stage 3a tumour 16 years earlier. Disease-specific 5 year survival for ENETS stages 1, 2a, 2b, 3a, 3b and 4 were 100, 100, 93, 100, 71, and 67% respectively. Overall 5 year survival mirrored these figures except for ENET stage 1 disease, where two non-NET related deaths occurred, hence survival of 92%. Significantly worse overall and disease-specific 5 year survivals occurred in ENETS stages 3b and 4 compared to others (P≤0.016).

Conclusion: Tumour size >2.0 cm remains prognostic for lymph node metastasis. GCC histology was not only prognostic for recurrence after aNET resection, but, also prognostic for residual disease along with grade ≥G2. We suggest that extended follow-up (10 years or more) is appropriate for patients with ENETS stage disease (3b and 4), GCC histology, or following R1 resection because of their higher rates of disease recurrence and poorer overall survival.