Purpose: Small intestinal neuroendocrine tumours (siNETs) with a Ki-67 proliferation index between 3 and 20% belong to WHO grade 2. Response to treatment may be monitored by blood chromogranin A (CgA) and urine 5-hydroxyindoleacetic acid (5HIAA). The aim of this retrospective study was to investigate the prognostic value of baseline CgA and 5HIAA and of the early biochemical response to treatment, and to compare different cut-off values used in the literature.

Methods: A retrospective cohort study of 184 patients with siNET Grade 2 treated with somatostatin analogues (SSA), interferon-alpha (IFN) or peptide receptor radionuclide therapy (PRRT).

Results: Baseline CgA was a statistically significant prognostic marker for both cancer-specific survival (CSS) and progression-free survival (PFS). A cut-off of 5 × ULN (upper limit of normal) was best discriminative in most cases, but 2 × ULN discriminated better for SSA. Baseline 5HIAA was a prognostic marker for CSS in treatment with IFN and PRRT, but not for single SSA. Early changes of CgA and 5HIAA correlated well with CSS (HR 3.18, 95% CI 1.82–5.56 and HR 1.47, 95% CI 1.16–1.86) and PFS (HR 3.08, 95% CI 1.86–5.10 and HR 1.37, 95% CI 1.11–1.68) for SSA, but not for PRRT.

Conclusions: Baseline CgA and to a lesser extent 5HIAA are associated with CSS irrespective of treatment used, and with PFS after PRRT, and 5 × ULN provides best discrimination in many, but not all, cases. Early reductions of CgA and 5HIAA are prognostic for treatment with SSA, but not PRRT.

Small intestinal neuroendocrine tumours (Si-NET) are often studied as a uniform group. Proliferation index Ki-67 influences prognosis and determines tumour grade. We hypothesized that Si-NET grade 2 (G2) tumours, which have a higher Ki-67 than G1 tumours, might benefit less from established treatments for metastatic disease. We conducted a retrospective cohort study of 212 patients with metastatic Si-NET G2 treated in two Swedish hospitals during 20 years (2000-2019). Median cancer-specific survival on first-line somatostatin analogues (SSA) was 77 months. Median progression-free survival (PFS) was 12.4 months when SSA was given as monotherapy and 19 months for all patients receiving first-line SSA. PFS after SSA dose escalation was 6 months in patients with radiological progression. Treatment efficacies of SSA and peptide receptor radionuclide treatment (PRRT) were studied separately in patients with Ki-67 of 3-5%, 5-10% and 10-20%. For SSA, PFS was significantly shorter at higher Ki-67 levels (31, 18 and 10 months, respectively), while there was only a minor difference in PFS for PRRT (29, 25 and 25 months). Median PFS for sequential treatment with interferon-alpha (IFN alpha), everolimus and chemotherapy was 6, 5 and 9 months. IFN alpha seemed to be effective in tumours with low somatostatin-receptor expression. In conclusion, established treatments appeared effective in Si-NET G2, despite their higher proliferation index compared to G1 tumours. However, efficacy of SSA but not PRRT was reduced at higher Ki-67 levels. SSA dose escalation provided limited disease stabilization.

Several inflammation scores have shown association with survival outcomes for patients with neuroendocrine tumours (NET) treated with peptide receptor radionuclide therapy (PRRT). However, whether these scores add value to established prognostic factors remains unknown. In this retrospective, cohort study of 557 NET patients undergoing PRRT in a tertiary referral centre from 2005 to 2015, we examined inflammatory markers and scores previously associated with cancer outcomes, using Cox proportional hazard models and Akaike's information criterion. Lower albumin (hazard ratio [95% confidence interval], .91 [.87-.95] per unit), as well as higher C-reactive protein (CRP; 1.02 [1.01-1.02]), Glasgow Prognostic Score (GPS; 1 vs. 0: 1.67 [1.14-2.44], 2 vs. 0 3.60 [2.24-5.79]), CRP/albumin ratio (1.84 [1.43-2.37]) and platelet count (Plt) x CRP, but not white blood cell, neutrophil and thrombocyte counts or derived neutrophil to lymphocyte ratio (dNLR), were associated with shorter median overall survival (OS) in an adjusted analysis. The addition of parameters based on albumin and CRP, but not dNLR, to a base model including age, chromogranin A, the cell proliferation marker Ki-67, performance status, tumour site and previous treatments improved the predictive accuracy of the base model. In an exploratory analysis of patients with available erythrocyte sedimentation rate (ESR) and CRP, ESR emerged as the most powerful predictor. When added to a prognostic model for OS in NET patients treated with PRRT, most inflammation scores further improved the model. Albumin was the single marker adding most value to the set of established prognostic markers, whereas dNLR did not seem to improve the model's prognostic ability.