Epidemiological study of gastroenteropancreatic neuroendocrine  tumors in Japan.
BACKGROUND
There have been few epidemiological studies on gastroenteropancreatic neuroendocrine tumors (GEP-NETs) in Japan.


METHODS
We examined the epidemiology of GEP-NETs [pancreatic endocrine tumors (PETs) and gastrointestinal neuroendocrine tumors (GI-NETs)] in Japan in 2005 using a nationwide stratified random sampling method.


RESULTS
A total of 2,845 individuals received treatment for PETs. Prevalence was estimated as 2.23/100,000 with an annual onset incidence of 1.01/100,000. Non-functioning tumor (NF)-PET constituted 47.4%, followed by insulinoma (38.2%) and gastrinoma (7.9%). Distant metastases were reported in 21% patients with NF-PETs and occurred more frequently as tumor size increased (>2 cm). Multiple endocrine neoplasia type 1 (MEN-1) was detected in 10% of PETs but only in 6.1% of NF-PETs. NF-PETs were detected incidentally by physical examination in 24% patients. In 2005, an estimated 4,406 patients received treatment for GI-NETs. Prevalence was estimated as 3.45/100,000, with an annual onset incidence of 2.10/100,000. The locations of GI-NETs varied: foregut, 30.4%; midgut, 9.6%; and hindgut, 60.0%. Distant metastases were observed in 6%. Lymph node metastases occurred more frequently as tumor size increased (>1 cm). The frequency of MEN-1 complications was 1%. Physical examination revealed GI-NETs in 44% patients. The frequency of symptomatic GI-NETs was 3.4%. Interestingly, 77.1% of patients with foregut GI-NETs had type A gastritis.


CONCLUSIONS
Our results show there are large differences in GEP-NETs between Japan and Western nations, primarily due to differences in the presence of MEN-1 in NF-PETs and the location, symptomatic status, and prevalence of malignancy in GI-NETs.
Ito
Tetsuhide
T
Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Sasano
Hironobu
H
Tanaka
Masao
M
Osamura
R Yoshiyuki
RY
Sasaki
Iwao
I
Kimura
Wataru
W
Takano
Koji
K
Obara
Takao
T
Ishibashi
Miyuki
M
Nakao
Kazuwa
K
Doi
Ryuichiro
R
Shimatsu
Akira
A
Nishida
Toshirou
T
Komoto
Izumi
I
Hirata
Yukio
Y
Nakamura
Kazuhiko
K
Igarashi
Hisato
H
Jensen
Robert T
RT
Wiedenmann
Bertram
B
Imamura
Masayuki
M
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D003625:Data Collection; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000453:epidemiology* / Q000473:pathology; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D018358:Neuroendocrine Tumors / Q000453:epidemiology* / Q000473:pathology; D010190:Pancreatic Neoplasms / Q000453:epidemiology* / Q000473:pathology; D015995:Prevalence; D055815:Young Adult