Reduction of the incidence and mortality of rectal cancer by polypectomy: a prospective cohort study in Haining County

Table 1 Age distribution of two groups of high-risk populations with polyps

Age Group	1a		2b		Total (%)
	Male (%)	Female (%)	Male (%)	Female (%)
30-	644 (36.6)	440 (41.6)	287 (34.4)	181 (37.2)	1552 (38.1)
40-	452 (25.7)	270 (25.6)	226 (27.1)	100 (23.7)	1049 (25.8)
50-	434 (24.7)	237 (22.4)	204 (24.4)	99 (23.5)	974 (23.9)
60-	164 (9.3)	89 (8.4)	99 (11.9)	37 (27.2)	389 (9.6)
70-	64 (3.7)	21 (2.0)	19 (2.3)	5 (1.2)	109 (2.7)
Total	1758	1057	835	422	4072

^a1: high-risk population with history of polyps identified during 1977-1978;

^b2: High-risk population identified in 1980. The age of 4 participants is unknewn

Table 2 Pathologic features of initial polyps of two groups of high-risk populations

Pathologic Diagnosis	First group		Second group		Total
	n	%	n	%	n	%
Adenoma	1485	52.88	876	69.47	2361	58.02
Tubular	1352	48.15	843	66.85	2195	53.94
Tublovillous	104	3.70	31	2.46	135	3.32
Villous	19	0.68	2	0.16	21	0.52
Non-adenomatus	1326	47.22	382	30.29	1708	41.98
Mucosal	596	21.23	95	7.53	691	16.98
Juvenile	183	6.52	95	7.53	278	6.83
Hyperplastic	113	4.02	72	5.71	185	4.55
Inflammatory	90	3.21	4	0.32	94	2.31
Schistosomiais	326	11.61	115	9.12	441	10.84
Lymphoid	10	0.36	1	0.08	11	0.27
Other	8	0.28	0	0.00	8	0.20
No pathologic diag	7	0.25	3	0.24	10	0.25
Total	2815		1261		4076

Table 3 Output of following with endoscopy among high-risk population with history of polyps

Year	Expected n	Observed n (%)	Adenoma n (%)	Non-adenomatous n (%)	Colorectal cancern (1/100000)
1st group
1979	2803	2197 (78.38)	178 (8.10)	104 (4.73)	6 (273.10)
1981	2763	1592 (57.62)	61 (3.83)	27 (1.70)	4 (251.26)
1983	2719	2147 (78.96)	108 (5.03)	33 (1.54)	2 (93.15)
1987*	2689	2408 (89.52)	191 (7.93)	96 (4.00)	4 (166.11)
1993*	2388	1475 (61.77)	121 (8.20)	52 (3.53)	4 (271.19)
1998*	2207	1020 (46.22)	95 (9.31)	17 (1.67)	4 (392.16)
2nd group
1982	1253	461 (36.79)	17 (3.69)	6 (1.30)	0 (0.00)
1984	1235	1056 (85.51)	49 (4.64)	26 (2.46)	0 (0.00)
1988*	1183	931 (78.70)	64 (6.87)	20 (2.15)	0 (0.00)
1994*	1097	479 (43.66)	33 (6.68)	17 (3.55)	3 (626.30)
1998*	1040	486 (46.73)	36 (7.41)	17 (3.50)	0 (0.00)
Total		1425	2953 (6.68)	417 (2.93)	27 (189.45)

^*Following with 60 cm flexible sigmoidoscopy since 1987