Colorectal cancer, including colon cancer and rectal cancer, is one of the most common malignant tumors in humans. Worldwide, the annual incidence of colorectal cancer is nearly 1 million, and the incidence rate is the third after lung cancer and breast cancer. According to statistics, there were about 148,610 new cases and 55,170 deaths of colorectal cancer in the United States in 2006, and the age-specific incidence rate of colorectal cancer in China in 2002 was 13.6/100,000 for men and 9.2/100,000 for women. From the incidence trend, although a few developed countries such as the United States in recent years, the incidence of colorectal cancer has a decreasing trend: 1.5% for men and 1.3% for women; but most countries, especially China, the incidence of colorectal cancer is increasing significantly: in the 1990s compared with the 1970s, the incidence rate in urban areas rose by 31.95% and in rural areas by 8.51%, and will steadily increase in the long period of time in the future. What is of concern is that the treatment effect of colorectal cancer has not improved much in the past 30 years, and the 5-year survival rate is only 50%-60%, so it is more important to improve the early diagnosis rate of colorectal cancer.
Recent clinical epidemiological data show that the clinical characteristics and incidence pattern of colorectal cancer have changed, so it is of great value to discuss the changes in the incidence pattern of colorectal cancer for the relevant departments to formulate prevention and treatment strategies and improve the early diagnosis of colorectal cancer.
Previous characteristics in China
①Younger age of prevalence;
②High proportion of rectal cancer;
③High proportion of young people
Age is a very important factor in the development of colorectal cancer. Previous data show that the age of prevalence of colorectal cancer in China is 12 to 18 years lower than that in western countries, and the median age of incidence is around 45 years.
Another major characteristic of colorectal cancer in China is that the preferred site is the rectum: a group of 3147 cases of colorectal cancer in the 1980s showed that rectal cancer accounted for 72.6%; while the proportion of rectal cancer in foreign countries was only about 28.5% during the same period.
The high proportion of young people with colorectal cancer was once considered a major feature of colorectal cancer in China. The proportion of young patients with colorectal cancer in China ranges from 3.5% to 22.7%, while the proportion abroad is generally about 1% to 4%. However, the age limit standard of young colorectal cancer has not been fully unified so far, and the age of young colorectal cancer in China is mostly 30 years old, while in foreign countries it is mostly 40 years old. In addition, the publication bias caused by the different weight of patients admitted to each medical unit may also be an important factor in the disparity of the proportion of young colorectal cancer at home and abroad.
Recent trends
①Age tends to be older;
②The site of incidence is shifting to the right;
③The proportion of female patients is increasing
Domestic and international studies have shown that the age of colorectal cancer incidence is gradually increasing, and the proportion of elderly colorectal cancer is increasing. This may be related to the increasing per capita life expectancy in each country and the increasing proportion of elderly people in the population. We summarized and analyzed the clinical data of 6501 cases of colorectal cancer patients in five tertiary hospitals in four major regions of Guangdong Province, including the Pearl River Delta, northern Guangdong, western Guangdong and eastern Guangdong, for 15 years from 1990 to 2004, and the results showed that the median age of colorectal cancer in the last 15 years increased from 55 years in the 1990s to 1992s to 61 years in the 2002-2004s, an increase of 6 years, which is consistent with the Guangdong The median age increased significantly when compared with previously reported data in the 1960s, 1970s and 1980s in Guangdong.
In 1966, Axetell et al. found a gradual rightward shift in the site of colorectal cancer incidence, which was subsequently confirmed by studies in many countries. In China, some data showed that the proportion of proximal colon cancer in all colorectal cancers increased by 4.3% in the 1990s compared with the 1980s. In addition, there is a close relationship between the distribution of colorectal cancer sites and age: American scholars found that proximal colon cancer accounted for only 18% of colorectal cancer patients under 30 years of age, but up to 28.6% of those over 80 years of age; Gonzalez et al. concluded from logistic regression analysis of factors affecting proximal distribution that the probability of proximal distribution increased by 2.2% for each year of age increase. The present data also showed that the proportion of right hemicolectomy in colorectal cancer increased by 11.7% in the early 21st century compared with the 1980s, and the proportion of right hemicolectomy increased with age, which was more obvious in women.
The increase in the proportion of women is also one of the epidemic trends of colorectal cancer in recent years. In China, some scholars summarized the literature of 10,201 cases of colorectal cancer in 1980s and 1990s, and found that the ratio of men to women in colorectal cancer decreased from 1.50:1 in 1980s to 1.26:1 in 1990s. female hormones may be one of the factors, because female hormones can affect cholesterol metabolism and consequently the production of bile acids, thus increasing the incidence of colorectal cancer in women.
Future response
Pay attention to the diagnosis and treatment of colorectal cancer in young people
Some domestic scholars believe that the incidence rate of colorectal cancer among young people in China has been decreasing in recent years. However, our data show that the proportion of young colorectal cancer (defined as ≤30 years old) has decreased from 7.1% (49/689) to 3.5% (81/2324) in recent 15 years, while the proportion of old colorectal cancer (>60 years old) has increased from 30.6% (211/689) to 51.5% (1196/2324), suggesting that the number of cases of young colorectal cancer patients has not decreased in recent 15 years, but only The proportion of colorectal cancer has decreased, which is caused by the rise of colorectal cancer in middle and old age.
Some studies have found that young colorectal cancer patients in Dukes’ A or Dukes’ B stage have better survival rates than other people in the same stage, which may be related to better surgical tolerance and adjuvant treatment effects in young people; on the other hand, young people diagnosed with Dukes’ C or On the other hand, young colorectal cancer patients diagnosed with Dukes’ C or Dukes’ D have similar or worse outcomes than middle-aged or older patients at the same stage, which may be related to their more aggressive pathological features.
Young colorectal cancer has a higher incidence of mucinous carcinoma (including indolent cell carcinoma) and hypofractionated carcinoma, which is one of the most important differences between young and middle-aged and older colorectal cancers. Mucinous carcinoma accounts for 21% of colorectal cancer patients in young people and 10%-15% in other colorectal cancer populations; hypofractionated carcinoma accounts for 27% in young people and 2%-29% in those >40 years old. Mucinous and hypofractionated cancers have poorer prognosis than highly and moderately differentiated cancers, resulting in lower 5-year survival rate of young colorectal cancer: 24.7% for mucinous cancer and 25.5% for hypofractionated cancer.
Griffin found that 68% of patients <40 years old had Dukes'C or Dukes'D metastases, and the prognosis was poor. Dukes' C or Dukes' D, a significantly higher percentage than in patients >40 years of age (32%-49.2%). In addition, the Marble study found that 85% of young people with hypofractionated colorectal cancer were in Dukes’ C or Dukes’ D stage, compared with only 15% of middle-aged and older people.
In conclusion, young colorectal cancer has relatively higher malignancy, early metastasis and poor prognosis, and it is not easy to attract the attention of patients and doctors, so it is easy to be misdiagnosed. However, if detected and diagnosed early, young colorectal cancer has a higher survival rate. Therefore, in formulating colorectal cancer prevention and treatment strategies, the relevant departments should pay special attention to the screening of suspicious symptoms in young people, early diagnosis and improved prognosis.
Full colonoscopy is increasingly important for screening, diagnosis and follow-up of colorectal cancer
Although sigmoidoscopy was once considered to be an effective screening tool for colorectal cancer, data show that if sigmoidoscopy alone can only detect about 80% of colorectal cancers, if it is calculated that about 25% of patients are not adequately revealed during sigmoidoscopy, then the leakage rate will further increase. Both domestic and international data show that colorectal cancer has a tendency to migrate to the right side, and our data support this, so whole colonoscopy is becoming increasingly important for screening, diagnosis and follow-up of colorectal cancer.
Sigmoidoscopy can only examine the distal colon, but not the proximal colon. Overseas studies have shown that a significant proportion of progressive proximal colon adenomas are not accompanied by distal colon adenomas and are therefore easily missed by sigmoidoscopy. In a study of 1,463 asymptomatic women undergoing colonoscopy, only 34.7% of patients with progressive tumors had distal colonic adenomas diagnosed by sigmoidoscopy; compared with men of the same age group from the Veterans Collaborative Administration, these men were more likely to have progressive tumors than women (8.6% vs. 4.5%), yet 66.3% of these men who were more likely to have progressive tumors could be diagnosed by sigmoidoscopy. However, 66.3% of these men who were more likely to have progressive tumors could be detected by sigmoidoscopy. In addition, because the incidence of proximal colon tumors increases with age, sigmoidoscopic screening appears to be more appropriate for men and those younger than 60 years of age.
Proximal colorectal cancer is more highly staged and has a worse prognosis than distal, which may be due to the delay in diagnosis due to the screening method, and the biology of the tumor itself. It has been found that proximal colorectal cancer is 10% more likely to be advanced than distal colorectal cancer patients at the time of presentation. The probability of advanced stage at the time of consultation increases by 4% for each site of movement from the rectum to the ileocecal region.
Colonoscopy allows for examination of the entire colon, which is much more extensive than sigmoidoscopy, and allows for direct visualization of the lesion and simultaneous biopsy and treatment. Together with pathology, colonoscopy is considered the gold standard for the diagnosis of colorectal cancer and is often used for re-screening when other screening methods are positive. Although no prospective randomized trials have shown that colonoscopy reduces mortality from colorectal cancer, studies of sigmoidoscopy may indirectly suggest the effectiveness of colonoscopy. Colonoscopy and treatment have been shown to reduce the incidence of colorectal cancer in patients with colorectal polyps. Compared with fecal occult blood testing and sigmoidoscopy, colonoscopy represents a more cost-effective method of colorectal cancer screening.
Therefore, the American Society for Gastrointestinal Endoscopy recently recommended colonoscopy as the preferred method for colorectal cancer screening and for further screening in patients with positive FOBT and sigmoidoscopy. The application of colonoscopy appears to be more necessary for symptomatic patients, especially the elderly and women.