Abstract
Background and aims In multiple endocrine neoplasia type 1 (MEN1), endoscopic ultrasound (EUS) is used
for identification and follow-up of pancreatic neuroendocrine tumors (PNETs). The
role of EUS in surveillance of small ( < 20 mm) PNETs is unclear, mostly because the
natural course of these lesions is largely unknown. We aimed to determine annual growth
and incidence rate of small PNETs in patients with MEN1 using EUS-based surveillance.
Patients and methods Linear array EUS procedures in patients with MEN1 between 2002 and 2015 were identified.
Number, size, and location of PNETs were recorded. Annual growth of PNETs < 20 mm
identified at the initial EUS (“prevalent” PNETs) and during follow-up (“incident”
PNETs) was calculated using mixed model linear regression analysis.
Results A total of 54 patients were identified and 38 patients were included. In all, 226
PNETs were identified (median size 5.0 mm, interquartile range 3.7 – 7.5) of which
124 (55 %) were prevalent and 102 (45 %) were incident PNETs. Annual incidence rate
was 0.79 PNETs/year (95 % confidence interval [CI] 0.73 to 0.87). Overall growth rate
was 0.10 mm/year (95 %CI 0.02 to 0.19; P = 0.01); PNETs < 10 mm (n = 198) did not grow (P = 0.23), whereas PNETs ≥ 10 mm (n = 28) grew 0.44 mm/year (95 %CI 0.10 to 0.78; P = 0.01). Prevalent PNETs grew 0.21 mm/year (95 %CI 0.10 – 0.32; P < 0.001), whereas incident PNETs did not grow (P = 0.26).
Conclusions The annual growth rate of small, solid PNETs in patients with MEN1 is lower than
previously thought. Surveillance intervals could probably be prolonged without compromising
safety.
