Grading of Neuroendocrine Carcinomas: Correlation of 68Ga-PETCT Scan with Tissue Biomarkers

Abstract EN

There is a growing need for more accurate biomarkers to facilitate the diagnosis and prognosis of patients with grade (G) 3 neuroendocrine carcinomas (NECs).

In particular, the discrimination between well-differentiated neuroendocrine carcinomas (WD-NECs) and poorly differentiated neuroendocrine carcinomas (PD-NECs) is still an unmet need.

We previously showed that 68Gallium-(68Ga-) PET/CT positivity is a prognostic factor in patients with gastroenteropancreatic (GEP) G3 NECs, correlating with a better outcome in terms of overall survival.

Here, we hypothesize that 68Ga-PET/CT could help to discriminate between WD-NECs and PD-NECs, adding complementary information to that obtained from morphologic and biologic factors.

A retrospective, single-institution study was performed on 11 patients with histologically confirmed, measurable G3 large- or small-cell GEP-NECs according to the 2017 WHO classification.

The staging procedures included a 68Ga-PET/CT scan.

Results of 68Ga-PET/CT were correlated in univariate analysis with loss of tissue immunohistochemical expression of DAXX/ATRX or RB1 frequently associated with WD-NECs or PD-NECs, respectively.

None of the patients with positive 68Ga-PET/CT showed loss of RB1 expression, whereas among those (n=6) with negative 68Ga-PET/CT, 4 showed loss of expression.

A trend towards a correlation between loss of RB1 expression and negative 68Ga-PET/CT was observed.

Our preliminary data support the hypothesis that PD-NECs carrying RB1 mutation and loss of its expression may be associated with negative 68Ga-PET/CT.

If confirmed in a larger clinical trial, 68Ga-PET/CT would help in the stratification of G3 NECs.