Risk factors for small intestinal adenocarcinomas that are common in the proximal small intestine

Table 1 Regions where small intestinal adenocarcinoma was reported

Country	Year	Number1	Duodenum		Jejunum		Ileum		Ref.
France	2020	347	210	60.6%	72	20.7%	65	18.7%	[31]
China	2020	42	112	26.2%	29	69.0%	2	4.8%	[15]
Japan	2015	47	14	29.8%	21	44.7%	12	25.5%	[32]
United States	2010	421	230	54.6%	142	33.7%	49	11.7%	[33]
China	2010	197	108	54.8%	59	29.9%	30	15.3%	[34]
United States	2006	460	272	59.1%	98	21.3%	90	19.6%	[35]
United States	2005	195	113	57.9%	54	27.7%	28	14.4%	[7]
United States	1996	1404	777	55.3%	376	26.8%	251	17.9%	[2]
Japan	Our cases	503	20	40.0%	26	52.0%	4	8.0%	N/A

¹Number excludes cases of unknown site.

²A total of 160 cases of primary cancer in the papilla of Vater were excluded.

³Only patients with a normal papilla of Vater were included.

N/A: Not applicable.