Growth rate of pancreatic neuroendocrine tumors in MEN1 syndrome; an EUS surveillance
study
C. Cottone1, G.D. Valk2, M.G. van Oijen1, P.D. Siersema1, F.P. Vleggaar1
1. Department of Gastroenterology and Hepatology; 2. Department of Internal Medicine, University
Medical Center Utrecht, Utrecht, the Netherlands
In multiple endocrine neoplasia type 1 (MEN1) syndrome, endoscopic ultrasonography (EUS) has
become the standard imaging technique for identifying and localizing pancreatic neuroendocrine
tumors (PNETs). For asymptomatic and small (<2 cm) PNETs, the role of EUS-based surveillance is
not clear, particularly because the natural course of these lesions is largely unknown. Our aim was to
asses the annual incidence and growth rates of small, asymptomatic PNETs in MEN1 syndrome as
assessed by EUS.
All patients with MEN1 syndrome who underwent EUS of PNETs in the period 2005 and 2011 in our
hospital, which is a national referral center for MEN1 syndrome, were reviewed. Follow-up EUS was
performed every 6-12 months while a CT, MRI or Somatostatin Receptor Scan (SRS) was performed
at first diagnosis.
In total 36 patients (males 67%, mean age 43 ±13 years) were included, in whom 107 PNETs were
found at the index EUS. PNETs were located in the pancreas caput in 27/107 (25%), confluence
caput/corpus in 5 (5%), corpus in 42 (39%), confluence corpus/tail in 9 (8%) and tail in 24 (22%).
Median diameter was 6.4 mm (range 2-24 mm) and 91 (85%) PNETs were ≤10 mm. Only 42 of 107
PNETs were also identified by other imaging techniques with a sensitivity of 20/38 (53%) for CT,
22/70 (31%) for MRI and 6/22 (27%) for SRS. Twenty-eight patients (100 PNETs; mean 3.6±3.3
PNETs/patient) had at least two consecutive EUS procedures (range 2-7) during a median follow-up
period of 22 months (range 4-51). Incidence rate was 1.32 PNETs per person year and the median
growth rate of lesions was 0.37 mm per year (range -6 mm to +10 mm). PNETs ≤10 mm (84%) had a
median growth rate of 0 mm per year (range -6 mm to +4.8 mm; IQR -0.19 to 0.8), while PNETs >10
mm (16%) had a median growth rate of 1.3 mm per year (range from -2.7 mm to +10 mm; IQR 0 to
2). During follow-up, 8 patients (29%) underwent surgery because of symptoms (n=3), lesions ≥20
mm (n=4) and metastases (n=1). No correlations were found between growth rate of PNETs and age
or sex.
Conclusion: EUS based pancreatic surveillance in a large, single-center cohort of MEN1 patients
demonstrates that the overall growth rate of PNETs is slow, although PNETs >10 mm seem to grow
faster than those ≤10 mm. Surveillance intervals for performing repeat pancreatic EUS should depend
on the size of a PNET found at the most recently performed EUS with an estimated interval of 2-3
years.