Characteristics of the study population and screening results
As shown in Table 1, a total of 53,152 subjects, 17,926 women (33.73%) and 35,226 men (66.27%), underwent a screening colonoscopy from 30 provinces, autonomous regions, municipalities and special administrative regions of China from January 2013 to December 2019. The average age was 50 years (SD, 9 years) for women and 48.80 years (SD, 8.47 years) for men.
The findings included colon polyps in 30.36% (n= 16137), colorectal cancer in 0.59% (n= 313), and other benign lesions in 11.28% (n=5994). No abnormalities were found in 61.73% of colonoscopies (n= 32,811). The prevalence of colonic polyps and multiple colonic polyps was higher in men than in women (21.54% vs. 14.69% and 14.14% vs. 5.21%, respectively). The prevalence of CRC was not significantly different between men and women (0.57% vs. 0.62%, P =0.440).
Colonoscopy findings
The histological analysis indicated that 5.42% of patients (n=2873) had hyperplastic polyps, 14.51% (n=7713) had adenomas, 0.3% (n =159) had high-grade intraepithelial neoplasia, 0.59% (n=313) had carcinoma, 1.23% (n = 653) had serrated adenomas and 9% (n=4783) had other benign lesions. Hyperplastic polyps were found in 6.39% (n=2250) of male and 3.49% (n=623) of female patients (P=0.000), adenomas in 17.14% (n=6035) of male and 9.36% (n=1678) of female patients (P=0.001), high-grade intraepithelial neoplasia in 0.34% (n=120) of male and 0.22% (n=39) of female patients (P=0.014), carcinoma in 0.57% (n=201) of male vs. 0.62% (n=112) of female patients (P=0.440), and serrated adenomas in 1.56%(n=548) of male and 0.59% (n=105) of female patients (P=0.000). Of the 14.51% (95% CI, 14.21%-14.81, n = 7,713) adenomas found, 3.04% (95% CI, 2.90%-3.19%, n = 1617) were classified as AAs.
Overall, the detection rates for CRCs, AAs, adenomas and serrated adenomas were 0.59%, 3.04%, 14.51% and 1.23%, respectively. Furthermore, we calculated that the numbers of colonoscopies to detect one CRC, AA, adenoma and serrated adenoma were 169, 33, 7 and 81, respectively, as shown in Fig 1.
Figure 2 shows that the detection rates for adenomas, AAs, CRCs and serrated adenomas increased with age and were higher for men than for women. For example, the detection rate of AAs in men aged 60–64 years was 6.35% (95% CI 5.35%-7.35%), which was significantly higher than that in women of the same age range (2.64%, 95% CI 1.85%-3.43%).
Regarding the anatomical location of CRCs and AAs, more neoplasms were identified in the distal colon than in the proximal colon. Among them, 78.8% of CRCs, 64.2% of AAs and 66.4% of AAs ≥10 mm were located in the distal colon. The anatomical location distribution of advanced colorectal adenoma is shown in Figure 3.
Prevalence and NNS for adenomas
The prevalence of adenomas was 17.14% (95% CI, 16.74%-17.53%) for men and
9.36% (95% CI, 8.94%-9.79%) for women (p<0.001) (Table 2). The prevalence of adenomas among 45- to 49-year-old men was 16.06% (95% CI, 15.28%-16.84%), which was higher than the prevalence among women in the same age group (7.77% [95% CI, 6.95%-8.59%]) but close to the prevalence among 65- to 69-year-old women (17.22% [95% CI, 14.52%-19.91%]). The prevalence of 19.75% (95% CI, 18.91%-20.61%) among 50- to 55-year-old men was greater than that in women of the same age group (9.47%, [95% CI, 8.60%-10.33%]).
The mean NNS to detect adenomas was 6.89 (95% CI, 6.75–7.04) for all individuals, 5.83 (95% CI, 5.70–5.97) for men, and 10.68 for women (95% CI, 10.21–11.19) (p<0.001). In 45- to 49-year-old women, NNS was nearly twice as high as in men at the same age (12.87 [95% CI, 11.64–14.39] vs. 6.23 [95% CI, 5.94–6.54]). Among 45- to 49-year-old men, the NNS was 6.23 [95% CI, 5.94–6.54], similar to that for women aged 65 to 69 years (5.81 [95% CI, 5.02–6.89]).
Prevalence and NNS for AAs
The prevalence of AAs in men was more than twice that in women (3.67% [95% CI, 3.47%-3.87%] vs. 1.81% [95% CI, 1.61%-2.00%], P <0.001). The prevalence of AAs in 45- to 49-year-old men was 3.17% [95% CI, 2.80%-3.55%], which was twice as high as that in women of the same age group (1.49% [95% CI, 1.12%-1.86%, P < 0.001), while a similar prevalence of 3.44% (95% CI, 2.14% to 4.75%) was found for women aged 65 to 69 years. The prevalence of 4.31% [95% CI, 3.88%-4.74%] in men aged 50–54 years was also more than twice that in women of the same age group (1.69% [95% CI, 1.31%-2.07%]).
The NNS to find an AA was 32.89 (95% CI, 31.35–34.48) for all individuals, 55.25 (95% CI, 50.00–61.11) for women, and 27.25 (95% CI, 25.84–28.82,P <0.001) for men (Table 2). In 45- to 49-year-old women, the NNS to find an AA was 67.11 (95% CI, 53.76–89.29) vs. 31.55 ([95% CI, 28.17–35.71]) for men (P <0.001). Men aged 45 to 49 years had a similar NNS as 65- to 69-year-old women (31.55 [95% CI, 28.17–35.71] vs. 29.07 [95% CI, 21.05–46.73]).
Prevalence and NNS for CRCs
Men had a similar prevalence of CRC compared with women (0.57% [95% CI, 0.49%-0.65%] vs. 0.62% [95% CI, 0.51%-0.74%], P=0.440). The prevalence of 1.76%[95% CI, 1.22%-2.31%] among 60- to 64-year-old men was slightly higher than that among women in the same age group (1.07%, [95% CI, 0.56%-1.57%]). The prevalence of CRC in 65- to 69-year-old men was 3.18% [95% CI, 2.06%-4.31%], which was similar to the prevalence among 70- to 74-year-old women (3.70%, [95% CI, 0.79%-6.62%]).
The mean NNSs for CRC were 169.49 (95% CI, 153.85–192.31) colonoscopies for all individuals, 175.44 (95% CI, 153.85–204.08) colonoscopies for men, and 161.29 (95% CI, 135.14–196.08) for women. The NNS for CRC in men aged 60–64 years was lower than that in women of the same age (56.82 [95% CI, 43.29–81.97] vs. 93.46 [95% CI, 63.69–178.57]).
Prevalence and NNS for serrated adenomas
The prevalence of serrated adenomas in men was more than twice as high as that in women (1.56% [95% CI, 1.43%-1.69%] vs. 0.59% [95% CI, 0.47%-0.70], P=0.000) (Table 3). Men had a significantly higher risk of detecting serrated adenomas than women. Similarly, the prevalence of serrated adenomas among 45- to 49-year-old men was twice as high as that among women in the same age group (1.39% [95% CI, 1.14%-1.64%] vs. 0.51% [95% CI, 0.29%-0.73%], P <0.001). The prevalence of serrated adenomas was three times higher in men aged 50–54 years than in women of the same age group (1.66% [95% CI, 1.39%-1.93%]和0.54% [95% CI, 0.33%-0.77%], p<0.001, respectively).
The NNS to detect a serrated adenoma was 81.30 (95% CI, 75.76–99.01) for all individuals, 64.10 (95% CI, 59.17–69.93) for men, and 169.49 (95% CI, 142.86–212.77) for women (Table 2). In 45- to 49-year-old women, the NNS was 196.08 (95% CI, 136.99–344.83) vs. 71.94 (95% CI, 60.98–87.72) for men (P=0.001). Men aged 50 to 54 years had a lower NNS than women of the same age group (60.24 (95% CI, 51.81–71.94) vs. 185.19 [95% CI, 129.87–303.03]).