Colon cancer is one of the common malignant tumors in China, according to the latest data released by the National Cancer Center, in 2015, there were 387,600 new cases of colon cancer in China, accounting for 9.87% of all malignant tumor incidences; 187,100 deaths caused by colon cancer, accounting for 8.01% of all malignant tumor deaths. More than 80% of patients are already in the middle and advanced stages when they are diagnosed.
The prognosis of colorectal cancer is closely related to the "three early" (early detection, early diagnosis, and early treatment), and the 5-year survival rate of early colorectal cancer can reach more than 90%, and the 5-year relative survival rate of extremely early cancer can be almost 100%, while the relative survival rate of 5 years of distant metastatic advanced colorectal cancer is only 14%.
Therefore, regular screening and timely inspection are important. So what are the current clinical methods of colon cancer screening?
01
The easiest method – stool testing
Stool detection is divided into two categories, one is fecal occult blood experiment, and the other is to detect molecular markers of epithelial cells, that is, fecal DNA testing.
The fecal occult blood test, or FIT test, is a test that detects human hemoglobin in a stool specimen with specific antibodies, suggesting possible intestinal pathology. Studies have shown that FIT screening can reduce colorectal cancer mortality by 52%. A fecal occult blood test may be done annually or every 2 years to screen for colorectal cancer, or colonoscopy if a positive result is present.
Recommendation: FIT is suitable for colorectal cancer screening, and its sensitivity to colorectal cancer diagnosis is high, but its sensitivity to precancerous lesions is limited. (Strong recommendation, GRADE evidence rating: Medium)
Fecal DNA testing, that is, multi-target fecal FIT-DNA testing, is a laboratory technique to detect DNA mutations in fecal exfoliation cells and combine WITH to form an individual comprehensive risk score, and for subjects whose comprehensive score exceeds a preset threshold, they are defined as high-risk groups and require colonoscopy. In 2014, a multi-target fecal FIT-DNA test was approved by the U.S. Food and Drug Administration (FDA) and was recommended for colorectal cancer screening by colorectal cancer screening guidelines in the United States.
At present, China also has multi-target FIT-DNA testing products approved by the State Drug Administration. However, the scope of application and long-term screening effect of related multi-target FIT-DNA products in colorectal cancer screening in Chinese populations still need to be confirmed in further large-sample population studies. In addition, multi-target FIT-DNA testing is more expensive and requires central laboratory testing, and its application in large-scale population colorectal cancer screening is not yet mature, and it is currently only recommended for subjects who prefer non-invasive screening techniques and have testing conditions.
Recommendation: Multi-target fecal FIT-DNA testing can be used for colorectal cancer screening under certain conditions and has a certain screening capacity for colorectal cancer and precancerous lesions. (Weak recommendation, GRADE evidence rating: low)
The advantages of stool testing are simple, safe, economical, and have achieved significant success in colorectal cancer screening, but the disadvantage is that it lacks a high degree of accuracy, so it is only used as a means of initial screening and is suitable for people who cannot undergo colonoscopy.
02
The most effective method is electronic colonoscopy
Electronic colonoscopy is a doctor through a slender and curved front end with a camera instrument, from the anus into the large intestine, the image is transmitted to the display through the optical fiber, in the high-definition lens of the complete inspection of the entire color of the colorectum, can show the true color of the intestinal mucosa, can observe the blood vessels, mucosa subtle changes and so on. An experienced doctor can detect polyps with a detection rate of more than 95%, and the detection rate of early cancer is greater than 96%; lesions of 1 to 2 mm can be distinguished; and the polyps found can be removed together, and for suspicious lesions, tissue biopsy can be taken to further clarify the pathological diagnosis.
Recommendation: Colonoscopy is the gold standard for colon cancer screening. (Strong recommendation, GRADE evidence rating: high)
However, due to factors such as intestinal preparation, doctor's experience, and equipment, missed diagnoses can also occur. Painless colonoscopy is currently available in most hospitals, allowing patients to complete the examination easily without any pain.
03
The safest method – simulated colonoscopy
Colon CT imaging technology, also known as "simulated colonoscopy", refers to the subject after intestinal preparation, with gas to fill and expand the clean colon, and then perform a supine position of the whole colon and prone position thin layer CT scan, the two-dimensional image obtained for three-dimensional reconstruction, so as to generate a three-dimensional image similar to the colonoscope into the intestine examination, and in this way to check the potential lesion technology, so it is also called "simulated colonoscopy". Studies have shown that the detection rate of simulated colonoscopy for colon cancer is 100%, the detection rate of polyps with >1cm is 91%, and the detection rate of polyps with 6 to 9 mm is 82%, right
The advantages of simulated colonoscopy are non-invasive, painless, convenient and safe, the sensitivity of cancer screens is high, and the radiation amount of radiation is lower than that of barium enemas. However, there are also some disadvantages, such as the high cost of examination, the high rate of missed diagnosis of polyps and flat meats less than 5 mm, and not many medical institutions can carry out this examination.
Recommendation: Colon CT imaging technology can be used for colorectal cancer screening under specific conditions, and has a certain screening capacity for colorectal cancer and precancerous lesions. (Weak recommendation, GRADE evidence rating: low)
04
The most direct method is a digital examination
A digital examination is a method in which a doctor wears gloves and sticks a finger into a patient's anus to check for a localized disease. An accurate digital rectal examination can roughly determine whether there are lesions in the anus and rectum 7 to 10 cm from the margin and the nature of the lesions. Two-thirds of rectal cancer occurs where the fingers can touch it. Notably, about 85% of cases of delayed diagnosis of rectal cancer are due to the absence of a digital examination.
Its advantage is simple, direct and effective, the disadvantage is that it can only examine the middle and lower rectum, which can be used as one of the screening methods for rectal cancer, but for full colonic screening, colonoscopy is still recommended as the main means.
Combined with clinical, fecal occult blood experiments combined with colonoscopy are currently the golden combination of simple, safe, economical and high diagnostic rates.
Key References:
1. Expert Consensus Opinion on early colorectal cancer screening process in China (2019, Shanghai)
2. Lin Yong, Wang Hong, Screening Patterns and Screening Methods of Colorectal Cancer, Chinese Journal of General Practitioners, 2017,16(05): 342-345
3. Guidelines for colorectal cancer screening and early diagnosis and early treatment in China (2020, Beijing)[J]. Chin J Oncology, 2021, 43(1):16-38.5
Source: Shandong Provincial Maternal and Child Health Hospital Digestive Endoscopy