Gastric cancer in Alaska Native people: A cancer health disparity

Table 1 Comparative epidemiology of gastric cancer in United States Non-Hispanic White and Alaska Native populations n (%)

	United States			P1 value
	Non-Hispanic White	Alaska Native-SEER	Alaska Native Hospital
Population (in millions)23	274.6	0.14	0.14
Cancer registry summary
Registry type (number)	Population based (SEER 18)	Population based (SEER 18)	Hospital based (1)
Years included	2006-2014	2006-2014	2006-2014
Incident cases	40717	164	132
Calculated incidence rate4
Male	12.1	26.7	22.8
Female	3.4	18.7	13.6
Gender				0.01
Male	30141 (74.0)	95 (57.9)	82 (62.1)
Female	10576 (26.0)	69 (42.1)	50 (37.8)
Age				< 0.00015
Median (yr)	69.2 ± 0.07	60.4 ± 1.3	59.9 ± 1.2
< 20-34	258 (0.6)	4 (2.4)	3 (2.3)
35-44	926 (2.3)	9 (5.5)	9 (6.8)
45-54	4150 (10.2)	44 (26.8)	39 (29.5)
55-64	9224 (22.7)	41 (25.0)	28 (21.2)
65-74	11089 (27.2)	38 (23.2)	30 (22.7)
75-84	10144 (24.9)	23 (14.0)	19 (14.4)
> 84	4927 (12.1)	5 (3.0)	4 (3.0)
Anatomic site				< 0.00017
Cardia	26387 (64.8)	38 (23.2)	22 (16.7)
GE JX	14502 (35.6)	14 (8.5)	12 (9.1)
Non-cardia	8659 (21.3)	86 (52.4)	80 (60.6)
Fundus	970 (2.4)	4 (2.4)	12 (9.1)
Body6	3726 (9.2)	52 (30.0)	33 (25.0)
Antrum	3483 (8.6)	22 (13.4)	18 (13.6)
Pylorus	480 (1.2)	11 (6.7)	17 (12.9)
Overlap (multifocal)	1523 (3.7)	9 (5.5)	27 (20.5)
Unspecified	4148 (10.2)	31 (18.9)	3 (2.3)
Histological appearance				< 0.00018
Adenocarcinoma, NOS	33,921 (83.3)	126 (76.8)	80 (60.6)
Linitis Plastica, AC	172 (0.4)	1 (0.6)	2 (1.5)
Mucinous, AC	626 (1.5)	3 (1.8)	5 (3.8)
Tubular, AC	168 (0.5)	1 (0.6)	1 (0.8)
Papillary, AC	91 (0.2)	1 (0.6)	1 (0.8)
Mixed Cell, AC	560 (1.4)	1 (0.6)	0 (0)
Signet Ring	5179 (12.7)	31 (18.9)	52 (39.4)
Stage				0.002
I	8901 (21.9)	35 (21.3)	28 (21.1)
II	5662 (13.9)	24 (14.6)	24 (18.0)
III	5327 (13.1)	14 (8.5)	14 (11.4)
IV	15323 (37.6)	75 (45.7)	66 (50.0)
Unspecified	5504 (13.5)	16 (9.8)	0 (0)

¹Bold type indicates statistical significance (P < 0.05), statistics were performed on SEER Non-Hispanic White and Hospital based Alaska Native populations;

²Population for US White 2010, US Census;

³Population for AK Native 2010, Alaska Department of Labor and workforce development;

⁴Incidence rates, per 100000 person years and are age-adjusted using the 2000 US standard population;

⁵Wilcoxon rank sum test;

⁶Body includes body, lesser curvature, and greater curvature;

⁷Chi-square test between Cardia, Non-Cardia, Overlapping, and Unspecified;

⁸Chi-square test between adenocarcinoma and Signet Ring. NOS: Not otherwise specified; AC: Adenocarcinoma; GE JX: Gastroesophageal junction; SEER: Surveillance and Epidemiology End Results Program (SEER) 18 dataset; AC: Adenocarcinoma; JX: Junction.

Table 2 Descriptive epidemiology of Alaska Native gastric cancer patients n (%)

	Overall	Female	Male
Patients	132	50 (37.9)	82 (62.1)
Mean age (yr)	59.8 ± 1.2	62.4 ± 2.0	58.2 ± 1.4
Histological type
Diffuse	75 (56.8)	29 (58.0)	46 (56.1)
Intestinal	51 (38.6)	16 (32.0)	35 (42.7)
NOS	6 (4.5)	5 (10.0)	1 (1.2)
Blood type
A+	55 (41.7)	23 (46.0)	32 (39.0)
AB+	8 (6.1)	3 (6.0)	5 (6.1)
B+	9 (6.8)	5 (10.0)	4 (4.9)
O+	30 (22.7)	10 (20.0)	20 (24.4)
Unknown	30 (22.7)	9 (18.0)	21 (25.6)
Histological appearance
Signet Ring	52 (39.4)	23 (46.0)	29 (35.4)
Adenocarcinoma	80 (59.8)	27 (54.0)	53 (64.6)
Linitis Plastica, AC	2 (2.5)	0 (0)	2 (3.8)
Mucinous, AC	2 (2.5)	0 (0)	2 (3.8)
Tubular, AC	1 (1.3)	0 (0)	1 (1.9)
Papillary	1 (1.3)	0 (0)	1 (1.9)
NOS, AC	75 (93.8)	27 (100)	46 (86.8)
Stage
I	28 (21.2)	8 (16.0)	20 (24.4)
II	24 (18.2)	6 (12.0)	18 (22.0)
III	14 (11.4)	4 (8.0)	10 (12.2)
IV	66 (50.0)	32 (64.0)	34 (41.5)
Grade
Well/moderately differentiated	35 (26.5)	9 (18.0)	26 (31.7)
Poorly differentiated	88 (66.7)	36 (72.0)	52 (63.4)
Unknown	9 (6.8)	5 (10.0)	4 (4.9)
Anatomic site
GE JX	12 (9.1)	5 (10.0)	7 (8.5)
Cardia	10 (7.6)	5 (10.0)	5 (6.1)
Fundus	12 (9.1)	6 (12.0)	6 (7.3)
Body	33 (25.0)	10 (20.0)	23 (28.0)
Antrum	18(13.6)	8 (16.0)	10 (12.2)
Pylorus	17 (12.9)	7 (14.0)	10 (12.2)
Overlap (multifocal)	27 (20.5)	9 (18.0)	18 (22.0)
Unspecified	3 (2.3)	0 (0)	3 (3.7)
Regions of Alaska
North	38 (28.8)	17 (34.0)	21 (25.6)
Interior	11 (8.3)	1 (2.0)	10 (12.2)
Southwest	40 (30.3)	15 (30.0)	25 (30.5)
Southcentral	40 (30.3)	17 (34.0)	23 (28.0)
Southeast	3 (2.3)	0 (0)	3 (3.7)
Treatment2
Chemotherapy only	40 (30.3)	12 (24.0)	28 (34.1)
Neoadjuvant	21 (15.9)	8 (16.0)	13 (15.9)
Adjuvant	12 (9.1)	4 (8.0)	8 (9.8)
Resection only	12 (9.1)	5 (10.0)	7 (8.5)
Neoadjuvant, resection, adjuvant	9 (6.8)	3 (6.0)	6 (7.3)
None	38 (28.8)	18 (36.0)	20 (24.4)
Metastasis site1
Omentum/peritoneium/diaphram	27 (41.5)	14 (43.8)	13 (38.2)
Liver	14 (21.5)	6 (18.8)	8 (23.5)
Lung	1 (1.5)	0 (0)	1 (2.9)
Bone	2 (3.1)	0 (0)	2 (5.9)
Ovary	6 (9.2)	6 (18.8)	0 (0)
Multiple Sites	15 (23.1)	6 (18.8)	10 (29.4)
Additional clinical and pathological variables
H. pylori	52 (41.3)	20 (41.7)	32 (41.0)
Chronic gastritis	101 (76.5)	38 (76.0)	63 (76.8)
GERD	51 (39.5)	18 (36.0)	33 (41.3)
Gastric ulcer	91 (68.9)	35 (70.0)	56 (68.3)
Tobacco	108 (81.8)	36 (72.0)	72 (87.8)
Family history GI cancer	38 (28.8)	16 (32.0)	21 (25.6)

¹Patients with stage 4 gastric cancer were used for analysis;

²Neoadjuvant and adjuvant treatments include chemotherapy and chemoradiation regimens based on NCCN guidelines. NOS: Not otherwise specified; AC: Adenocarcinoma; GE JX: Gastroesophageal junction; H. pylori: Helicobacter pylori; GERD: Gastroesophageal reflux disease; GC: Gastric cancer.

Table 3 Univariate analysis of Alaska Native gastric cancer patients to identify variables associated with overall survival

	HR1	95%CI	P2 value
Age, ≥ 55 yr vs < 55 yr	0.73	0.49-1.07	0.11
Sex, male vs female	0.86	0.59-1.27	0.45
Geographical Region			0.53
North	1.00
Interior	0.99	0.50-1.96
Southwest	0.68	0.42-1.11
Southcentral	1.00	0.61-1.62
Southeast	0.65	0.15-2.69
Signet ring, present or absent	0.78	0.52-1.17	0.22
Diffuse vs intestinal	1.01	0.68-1.49	0.97
Anatomic site			0.07
Noncardia Cardia	1.00
Cardia3	1.10	0.66-1.84
Overlap/NOS	1.74	1.08-2.81
Grade			0.22
Poorly differentiated	1.00
Well/moderately	0.70	0.66-1.84
Unknown	0.82	0.37-1.84
AJCC Stage			< 0.0001
I	1.00
II	1.42	0.74-2.75
III	1.67	0.79-3.54
IV	4.91	2.80-8.61
Treatment4			< 0.0001
Chemo	1.00
None	2.07	1.29-3.32
Neoadjuvant, surgery	0.23	0.12-0.45
Surgery only	0.29	0.14-0.61
Surgery, adjuvant	0.27	0.13-0.59
Neoadjuvant, surgery, adjuvant	0.15	0.06-0.39
No. of nodes examined, ≥ 15 vs < 155 nodes3	0.37	0.19-0.75	< 0.0001
Blood Type			0.04
A+	1.00
AB+	0.88	0.42-1.82
B+	1.72	0.76-3.96
O+	1.78	1.05-3.01
Unknown	2.35	1.24-4.45
Multiple primaries, yes vs no	0.73	0.45-1.17	0.22
Tobacco			0.51
Yes	1.00
None	0.83	0.49-1.42
Chew/Iqmik	0.78	0.31-1.95
Former user6	1.26	0.80-1.97
Gastric ulcer, yes vs no	1.02	0.67-1.54	0.93
Chronic Gastritis, yes vs no	0.62	0.39-0.98	0.04
H. pylori, tumor positive vs negative	0.90	0.61-1.34	0.62
GERD, yes vs no	0.75	0.51-1.13	0.17

¹Univariate analysis was performed using Kaplan-Meier analysis model and log-rank test;

²Bold type indicates statistical significance (P < 0.05);

³Cardia includes gastroesophageal junction and cardia gastric cancers;

⁴Neoadjuvant and adjuvant treatments include chemotherapy and chemoradiation regimens based on NCCN guidelines;

⁵Patients that had a resection were included in analysis;

⁶Patients discontinued smoking before time of diagnosis. HR: Hazard ratio; CI: Confidence interval; AJCC: American Joint Committee on Cancer; Chemo: Chemotherapy; H. pylori: Helicobacter pylori; GERD: Gastroesophageal reflux disease.

Table 4 Multivariable Cox regression analysis for variables associated with overall survival

	HR	95%CI	P1 value
AJCC stage			0.004
I	1.00
II	1.59	0.74-3.32
III	3.09	1.32-7.27
IV	3.08	1.53-6.19
Treatment			0.007
Chemotherapy	1.00
None	2.80	1.57-5.00
Neoadjuvant, surgery	0.28	0.10-5.31
Surgery only	0.48	0.15-12.61
Surgery, adjuvant	0.19	0.06-5.17
Neoadjuvant, surgery, adjuvant	0.18	0.5-5.31
Blood type			0.160
A+	1.00
AB+	0.81	0.34-2.23
B+	1.01	0.45-2.24
O+	1.40	0.84-2.54
Unknown	0.63	0.31-1.17
Chronic gastritis, yes vs no	1.01	0.59-1.69	0.970

¹Bold type indicates statistical significance (P < 0.05). HR: Hazard ratio; CI: Confidence interval; AJCC: American Joint Committee on Cancer.