Colorectal Cancer Screening and Early Diagnosis and Treatment Protocol (2024 Edition)

Colorectal cancer is a relatively common malignancy that seriously threatens the health of Chinese residents. Studies have shown that conducting screening and early diagnosis and treatment among high-risk populations for colorectal cancer can effectively raise the early diagnosis rate and reduce mortality. To further standardize the work of colorectal cancer screening and early diagnosis and treatment and improve the effectiveness of colorectal cancer prevention and control, this protocol is hereby formulated.

I. Epidemiology

Relevant surveillance data show that in 2022 there were 517,100 new cases of colorectal cancer in China, accounting for 10.7% of all malignant tumor incidences. There were 240,000 deaths from colorectal cancer, accounting for 9.3% of all malignant tumor deaths. The national incidence and mortality rates of colorectal cancer were 36.63/100,000 and 17.00/100,000 respectively, and both are generally on the rise. Although the 5-year survival rate of colorectal cancer patients in China has improved in recent years, it remains at a relatively low level. If the disease can be detected and treated early, the 5-year survival rate will be significantly improved.

The main risk factors for colorectal cancer include intake of red meat and processed meat, alcohol consumption, smoking, obesity, diabetes, inflammatory bowel disease, and a family history of colorectal cancer. The main protective factors include intake of dietary fiber and dairy products, and reasonable physical exercise.

II. High-Risk Populations

(1) High-risk population for sporadic colorectal cancer

The risk of sporadic colorectal cancer is scored by combining age, sex, family history of colorectal cancer in first-degree relatives, smoking, and body mass index (BMI), according to the following criteria:

1. Age: ≤49 years (0 points), 50-59 years (1 point), ≥60 years (2 points).

2. Sex: female (0 points), male (1 point).

3. Smoking history: none (0 points), present (1 point).

4. BMI: <23 kg/m² (0 points), ≥23 kg/m² (1 point).

5. First-degree relatives (parents, children, and siblings) diagnosed with colorectal cancer: none (0 points), present (1 point; if one first-degree relative was diagnosed with colorectal cancer before the age of 60, or two first-degree relatives were diagnosed with colorectal cancer, 4 points).

Those with a cumulative score of ≥4 points are regarded as the high-risk population.

(2) High-risk population for hereditary colorectal cancer

People with Lynch syndrome or familial adenomatous polyposis, among others.

III. Screening

(1) Screening subjects

1. The high-risk population for sporadic colorectal cancer with no prior history of colorectal cancer is recommended to be screened between the ages of 40 and 74. Among them, those with one first-degree relative diagnosed with colorectal cancer before the age of 60, or with two or more first-degree relatives diagnosed with colorectal cancer, are recommended to begin screening 10 years earlier than the age at which the earliest affected first-degree relative was diagnosed, with no lower age limit for screening initiation.

2. Hereditary high-risk populations are advised to begin screening according to the following rules:

High-risk individuals with Lynch syndrome caused by MLH1 (MutL homolog 1)/MSH2 (MutS homolog 2) mutations should begin colonoscopy screening at age 20-25, or 2-5 years earlier than the age at onset of the youngest affected family member. High-risk individuals with Lynch syndrome caused by MSH6 (MutS homolog 6)/PMS2 (PMS1 homolog 2) mutations should begin colonoscopy screening at age 30-35, or 2-5 years earlier than the age at onset of the youngest affected family member. High-risk individuals from familial adenomatous polyposis kindreds should begin colonoscopy screening at age 10, undergo colonoscopy once a year, and continue for life.

(2) Screening methods

Colonoscopy is recommended as the first-line screening method. Those who cannot tolerate or are non-adherent to the first-line method may choose alternative methods such as immunochemical or chemical fecal occult blood testing, sigmoidoscopy, CT colonography, or multitarget stool DNA testing.

(3) Screening frequency

1. Routine screening frequency: colonoscopy every 5-10 years; for those with no lesions detected, the repeat colonoscopy interval may be 10 years. Fecal occult blood testing once a year.

2. For adenomas with a diameter ≥1 cm, adenomas with villous architecture ≥25% (i.e., villous or mixed adenomas), and other lesions accompanied by high-grade intraepithelial neoplasia: repeat colonoscopy within 1 year after treatment; if no abnormalities are found, subsequent repeat colonoscopy intervals may be extended to 3 years.

3. For other adenomas: repeat colonoscopy within 3 years after diagnosis and treatment; if no abnormalities are found, subsequent repeat colonoscopy intervals may be extended to 5 years.

4. For other benign intestinal lesions: because the increase in colorectal cancer risk is not significant, they may be managed as the general population. The repeat colonoscopy interval may be 10 years.

5. For inflammatory bowel diseases such as ulcerative colitis and Crohn's disease: repeat colonoscopy every 2 years after a confirmed diagnosis. If high-grade intraepithelial neoplasia is found during screening, repeat colonoscopy annually after treatment.

IV. Principles of Early Diagnosis and Treatment

Colorectal cancer should be diagnosed and treated as early as possible. All adenomas and polyps, especially precancerous lesions and patients with colorectal cancer, are advised to receive standardized treatment promptly. Colorectal precancerous lesions include adenomas with a diameter ≥10 mm, adenomas with villous architecture ≥25% (i.e., villous or mixed adenomas), and other lesions accompanied by high-grade intraepithelial neoplasia. Histopathology is the gold standard for diagnosing colorectal tumors, and a histopathological diagnosis should be obtained whenever possible. Clinical staging methods include contrast-enhanced CT of the chest, abdomen, and pelvis; depending on available medical resources, ultrasound, chromoendoscopy with magnification, endoscopic ultrasound (EUS), MRI, and PET-CT may also be chosen for imaging evaluation. Clinical and pathological staging refers to the Union for International Cancer Control (UICC) TNM staging system (8th edition).

(1) Treatment of early colorectal tumors amenable to endoscopic resection

For minute lesions with a diameter below 5 mm, cold snare polypectomy is recommended, and forceps biopsy removal may also be considered. For small lesions with a diameter of 6-9 mm, snare polypectomy, especially cold snare polypectomy, is recommended; endoscopic mucosal resection may also be considered. For raised lesions (pedunculated, subpedunculated, or sessile) larger than 10 mm in diameter, an appropriate snare is recommended according to the pedicle characteristics. For flat lesions (superficial elevated, superficial flat, superficial depressed) that can be completely removed in one piece, as well as some sessile lesions, endoscopic mucosal resection is recommended. In principle, the maximum diameter of lesions that can be resected en bloc in one session by endoscopic mucosal resection should not exceed 20 mm.

For lesions larger than 20 mm in maximum diameter that are difficult to completely resect in one session by endoscopic mucosal resection, lesions with a non-lifting sign, lesions smaller than 20 mm but endoscopically suspected of malignant transformation, residual or recurrent lesions larger than 10 mm after endoscopic mucosal resection that are difficult to treat with repeat endoscopic mucosal resection, and polyps suspected of malignancy but excluding deep submucosal invasion, endoscopic submucosal dissection is recommended.

(2) Treatment of colorectal tumors not amenable to endoscopic resection

For colorectal tumors for which preoperative evaluation indicates they are beyond the indications for endoscopic resection, and for patients requiring additional surgery after pathological assessment following endoscopic resection, the specific surgical approach and resection scope should be determined by comprehensive consideration of the tumor's location, size, the patient's surgical tolerance, and the patient's wishes.

The treatment principle for colorectal tumors not amenable to endoscopic resection is to operate whenever possible, and to select comprehensive treatment such as radiotherapy, chemotherapy, immunotherapy, and targeted therapy according to the postoperative pathological stage. For patients who cannot undergo surgery, comprehensive treatment is provided; for detailed diagnosis and treatment recommendations, please refer to the latest edition of the colorectal cancer diagnosis and treatment guidelines formulated and issued by the National Health Commission.

V. Follow-up and Management

In principle, all screened subjects should be followed up at least once a year to promptly obtain final diagnostic results and outcome information. For those with negative screening results, health education should be provided regarding their high-risk factors, and they should be reminded to undergo regular screening as required. For patients with precancerous lesions or colorectal cancer detected through screening, treatment and follow-up are recommended according to clinical diagnosis and treatment requirements.