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.

Table 2 Risk factors for small intestinal adenocarcinoma

Factor	Disease	Risks of small intestinal adenocarcinoma	Ref.
Animal fat		Correlation coefficient of 0.61	[21]
Animal protein		Correlation coefficient of 0.75	[21]
		2–3-fold higher risk	[36]
Bile salts		Bile salts may transform into carcinogenic deoxycholic acid	[22]
Hereditary polyposis	FAP	APC mutation; 5% is small bowel adenocarcinoma and half is duodenal adenocarcinoma	[27]
		The incidence is 330 times higher than that in the general population	[28]
	HNPCC	MMR gene mutation; lifetime risk is at approximately 1% in a French registry	[29]
	PJS	STK11 mutation; incidence is 520 times higher than that in the general population	[30]
Disease	Crohn’s disease	The incidence is 17.4 times higher than that in the general population	[37]
		The incidence is almost 3 times higher than that in the average American	[38]
	Celiac disease	It is implicated in 8%-13% of small bowel adenocarcinoma cases	[39,40]

FAP: Familial adenomatous polyposis; APC: Adenoma polyposis coli; HNPCC: Hereditary nonpolyposis colorectal cancer; MMR: Mismatch repair: PJS: Peutz-Jeghers syndrome; STK 11: Serine/threonine kinase 1.