Genome-Wide Association Study Identifies 4 Novel Risk Loci for Small Intestinal Neuroendocrine Tumors Including a Missense Mutation in LGR5

BACKGROUND & AIMS

Small intestinal neuroendocrine tumor (SI-NET) is a rare disease, but its incidence has increased over the past 4 decades. Understanding the genetic risk factors underlying SI-NETs can help in disease prevention and may provide clinically beneficial markers for diagnosis. Here the results of the largest genome-wide association study of SI-NETs performed to date with 405 cases and 614,666 controls are reported.

METHODS

Samples from 307 patients with SI-NETs and 287,137 controls in the FinnGen study were used for the identification of SI-NET risk-associated genetic variants. The results were also meta-analyzed with summary statistics from the UK Biobank (n = 98 patients with SI-NET and n = 327,529 controls).

RESULTS

We identified 6 genome-wide significant (P < 5 × 10-8) loci associated with SI-NET risk, of which 4 (near SEMA6A, LGR5, CDKAL1, and FERMT2) are novel and 2 (near LTA4H-ELK and in KIF16B) have been reported previously. Interestingly, the top hit (rs200138614; P = 1.80 × 10-19) was a missense variant (p.Cys712Phe) in the LGR5 gene, a bona-fide marker of adult intestinal stem cells and a potentiator of canonical WNT signaling. The association was validated in an independent Finnish collection of 70 patients with SI-NETs, as well as in the UK Biobank exome sequence data (n = 92 cases and n = 392,814 controls). Overexpression of LGR5 p.Cys712Phe in intestinal organoids abolished the ability of R-Spondin1 to support organoid growth, indicating that the mutation perturbed R-Spondin-LGR5 signaling.

CONCLUSIONS

Our study is the largest genome-wide association study to date on SI-NETs and reported 4 new associated genome-wide association study loci, including a novel missense mutation (rs200138614, p.Cys712Phe) in LGR5, a canonical marker of adult intestinal stem cells.

Pancreatic imaging in MEN1-Comparison of conventional and SSTR PET/CT imaging in real-life setting

OBJECTIVE

Pancreatic neuroendocrine tumors (panNETs) are the leading cause of death in patients with multiple endocrine neoplasia type 1 (MEN1). The role of somatostatin receptor positron emission tomography (SSTR PET/CT) in MEN1 has not been established. The aim was to assess pancreatic imaging in MEN1 in a real-life setting.

DESIGN AND METHODS

Fifty-eight patients with MEN1 (median age 40 (range 16-72) years) underwent SSTR PET/CT imaging; either as a screening tool regardless of disease stage (n = 47) or to further characterize known panNETs (n = 11). SSTR PET/CT and matched conventional imaging were blindly analyzed. We assessed the findings and the impact of SSTR PET/CT during a median follow-up of 47 months.

RESULTS

SSTR PET/CT detected three times as many panNETs as conventional imaging (p < 0.001). SSTR PET/CT altered the management of 27 patients (47%). Seven patients (12%) were referred for surgery, and five (9%) received systemic treatment. In 15/25 (60%) patients with no previous panNET (n = 22) or in remission after surgery (n = 3), SSTR PET/CT identified a panNET (n = 14) or recurrence (n = 1). In eight patients, SSTR PET/CT revealed a panNET not immediately visible on conventional imaging. During a median follow-up of 47 months, three became visible on conventional imaging, but none required intervention. When SSTR PET/CT was negative, no panNETs were identified on conventional imaging during 38 months of follow-up.

CONCLUSIONS

SSTR PET/CT demonstrates high accuracy in the detection of panNETs and alters the clinical management in nearly half of the MEN1-patients. SSTR PET/CT enables timely diagnosis and staging of MEN1-related panNETs.

Arterial function, biomarkers, carcinoid syndrome and carcinoid heart disease in patients with small intestinal neuroendocrine tumours

PURPOSE

Carcinoid heart disease (CHD) is a life-threatening complication of carcinoid syndrome (CS) characterised by tricuspid regurgitation (TR). However, there is an unmet need for earlier diagnosis of CHD. We cross-sectionally assessed the prevalence and potential predictive or diagnostic markers for CS and CHD in a contemporary cohort of patients with small intestinal neuroendocrine tumours (SI-NETs).

METHODS

Biochemical characteristics, hepatic tumour load, measures of arterial and endothelial function, atherosclerosis, and transthoracic echocardiography were analysed in a prospective cross-sectional setting.

RESULTS

Among the 65 patients studied, 29 (45%) had CS (CS+ ), and 3 (5%) CHD. CS+ was characterised by significantly higher hepatic tumour load, S-5-HIAA and fP-CgA, higher frequency of diarrhoea and flushing, and more frequent PRRT compared to CS- (for all, P < 0.05). Central systolic, central mean, and central end-systolic blood pressures were significantly higher in CS+ than in CS- (for all, P < 0.05). Subjects with grades 2-4 TR had higher hepatic tumour burden, fP-CgA, and S-5-HIAA compared to those with grades 0-1 TR, but measures of vascular function did not differ. fP-CgA (P = 0.017) and S-5-HIAA (P = 0.019) but not proBNP increased significantly according to the severity of TR.

CONCLUSION

Although CS is common, the prevalence of CHD was found to be lower in a contemporary cohort of SI-NET patients than previously anticipated. Measures of arterial or endothelial function or carotid atherosclerosis do not identify subjects with mild TR. Echocardiography remains the most sensitive means to diagnose CHD in CS patients with high tumour burden and elevated CgA and 5-HIAA.

Adrenocortical carcinoma: presentation and outcome of a contemporary patient series

BACKGROUND

Adrenocortical carcinoma (ACC) is a rare endocrine carcinoma with poor 5-year survival rates of < 40%. According to the literature, ACC is rarely an incidental imaging finding. However, presentation, treatment and outcome may differ in modern series.

DESIGN AND METHODS

We studied all patients (n = 47, four children) from a single centre during years 2002-2018. We re-evaluated radiologic and histopathological findings and assessed treatments and outcome. We searched for possible TP53 gene defects and assessed nationwide incidence of ACC.

RESULTS

In adults, incidental radiologic finding led to diagnosis in 79% at median age of 61 years. ENSAT stage I, II, III and IV was 19%, 40%, 19% and 21%, respectively. Nonenhanced CT demonstrated > 20 Hounsfield Units (HU) for all tumours (median 34 (21-45)), median size 92 mm (20-196), Ki67 17% (1-40%), Weiss score 7 (4-9) and Helsinki score 24 (4-48). ACC was more often found in the left than the right adrenal (p < 0.05). One child had Beckwith-Wiedemann and one a TP53 mutation. In adults, the primary tumour was resected in 88 and 79% received adjuvant mitotane therapy. Median hospital stay was significantly shorter in the laparoscopic vs. open surgery group (4 (3-7) vs. 8 (5-38) days, respectively; p < 0.001). In 3/4 patients, prolonged remission of > 5 to > 10 years was achieved after repeated surgery of metastases. Overall 5-year survival was 67%, and 96% vs. 26% for ENSAT stage I-II vs. III-IV (p < 0.0001). ENSAT stage and Ki67 predicted survival, type of surgery did not. Mitotane associated with better survival.

CONCLUSIONS

Contemporary ACC predominantly presents as an incidental imaging finding, characterised by HU > 20 on nonenhanced CT but variable tumour size (20-196 mm). Malignancy cannot be ruled out by small tumour size only. The 5-year survival of 96% in ENSAT stage I-III compares favourably to previous studies.