Survival in patients with neuroendocrine tumours of the small intestine: Nomogram validation and predictors of survival

Neuroendocrine tumours of the small intestine (SI‐NETs) are rare and heterogeneous. There is an unmet need for prognostication of disease course and to aid treatment strategies. A previously developed nomogram based on clinical and tumour characteristics aims to predict disease‐specific survival (DSS) in patients with a SI‐NET. We aimed to validate the nomogram and identify predictors of survival. Four hundred patients with a grade 1 or 2 SI‐NET were included, between January 2000 and June 2016. Predicted 5‐ and 10‐year survival was compared to actual DSS. Multivariable analysis identified predictors for actual DSS. We found that in low‐, medium-and high‐risk groups 5‐year nomogram DSS vs. actual DSS was 0.86 vs. 0.82 (p < 0.001), 0.52 vs. 0.71 (p < 0.001) and 0.26 vs. 0.53 (p < 0.001), respectively. Ten‐year nomogram DSS vs. actual DSS was 0.68 vs. 0.69 (p < 0.001), 0.40 vs. 0.50 (p < 0.001) and 0.20 vs. 0.35 (p < 0.001), respectively. Age, WHO‐performance score of 2, Ki‐67 index ≥10, unknown primary tumour, CgA > 6x ULN and elevated liver tests were identified as independent predictors for a worse DSS. This shows that the nomogram was able to differentiate, but underestimated DSS for patients with a SI‐NET. Improvement of prognostication incorporating new emerging biomarkers is necessary to adequately estimate survival.