Science Popularization | Scientific Cancer Prevention Starts with Physical Examination

A routine physical examination is not the same as cancer screening. Routine physicals focus on basic health indicators such as blood pressure, electrocardiogram, blood glucose, blood lipids, and liver and kidney function. Their main purpose is to screen for chronic diseases like hypertension, diabetes, and hyperlipidemia. They have low sensitivity for early-stage cancer and cannot capture cancer signals. Cancer screening, by contrast, is targeted testing for cancer, with the core goal of detecting early-stage cancer or precancerous lesions, making early detection, early diagnosis, and early treatment possible. For example, a routine chest X-ray can hardly detect tiny pulmonary nodules, whereas the core method for lung cancer screening is low-dose spiral CT. Routine abdominal ultrasound cannot accurately capture early features of liver cancer; it needs to be combined with alpha-fetoprotein testing and liver ultrasound. The purposes, items, and accuracy of the two types of examinations are fundamentally different, so they should not be used interchangeably.

Cancer screening items also differ for different populations. For healthy adults aged 18 and above, an annual health checkup is recommended. Core items should include a health self-assessment questionnaire to understand the examinee’s basic health status, conduct a preliminary risk assessment, and reasonably arrange examination items; routine laboratory tests such as complete blood count, urinalysis, and routine stool test plus occult blood test for initial screening of infection, gastrointestinal bleeding, and other risks; biochemical tests such as liver function, kidney function, blood lipids, blood glucose, serum uric acid, and homocysteine to evaluate metabolism and organ function; abdominal ultrasound of the liver, gallbladder, pancreas, spleen, and both kidneys, as well as thyroid ultrasound, for initial detection of nodules, masses, cysts, stones, and other abnormalities; and physical examination covering internal medicine, surgery, ophthalmology, otorhinolaryngology, and other areas to screen for abnormalities in basic organs.

For high-risk groups of some high-incidence cancers, screening and prevention recommendations are more specific. For lung cancer, high-risk groups include smokers; patients with chronic obstructive pulmonary disease; those with at least 1 year of occupational exposure to asbestos, ammonia, uranium, cadmium, coal smoke and soot, and similar agents; and those with more than 20 years of passive smoking, including former smokers with a history of at least 30 pack-years who have quit for less than 15 years. Screening uses low-dose chest CT. If no obvious abnormality is found, low-dose chest CT should be repeated annually. Prevention includes tobacco control; avoidance of exposure to risk factors; avoidance of indoor and outdoor air pollution; and use of range hoods when cooking, with less stir-frying at high temperature and less deep-frying.

For colorectal cancer, high-risk groups include males; people aged 45 years and above; smokers, including those who have quit; people with a body mass index of at least 24; those with a history of colorectal polyps; those with a family history of colorectal cancer in first-degree relatives; and those with familial adenomatous polyposis or Lynch syndrome. It is recommended that people aged 45 and above complete a colorectal cancer risk assessment questionnaire first, followed by simple colorectal cancer screening such as fecal occult blood test or colonoscopy. Prevention includes regular physical exercise and avoidance of obesity; a healthy diet with increased intake of crude fiber and fresh fruit; avoidance of high-fat and high-protein diets; quitting smoking and limiting alcohol; and reducing long-term inflammatory irritation of the digestive tract.

For liver cancer, high-risk groups include males aged 45 to 74 and females aged 50 to 74 who meet any of the following conditions: hepatitis B virus carriers, a history of hepatitis C virus infection, a history of liver cirrhosis, or a family history of liver cancer in first- or second-degree relatives. High-risk groups are advised to undergo serum alpha-fetoprotein testing and abdominal color Doppler ultrasound. Prevention includes receiving hepatitis B vaccination; quitting smoking and limiting alcohol; maintaining a healthy weight; promptly treating and controlling metabolic diseases; and not eating moldy foods such as moldy peanuts and corn, in order to avoid aflatoxin exposure.

For cervical cancer, high-risk groups include those infected with high-risk HPV; those with HIV infection or a history of sexually transmitted diseases; those who started sexual activity too early or have multiple sexual partners; smokers; and those who have previously received treatment for cervical precancerous lesions. For women with a history of sexual activity or married women, the recommended starting age for screening is 25 to 30 years, with cytological examination every 3 years. Women with HIV infection or immunocompromised conditions may start earlier as appropriate. Prevention includes receiving HPV preventive vaccines; avoiding high-risk sexual behavior; delaying the age of first sexual activity; not smoking or quitting smoking; and actively preventing and treating chronic cervicitis and other diseases.

For gastric cancer, high-risk groups include older people, with risk increasing with age; those with Helicobacter pylori infection; those with a high-salt diet, smoked and fried foods, and excessive intake of red meat and processed meat; those with long-term unhealthy eating habits such as skipping breakfast, irregular meals, eating too quickly, binge eating, eating leftovers, and insufficient fruit and vegetable intake; smokers and alcohol drinkers; those with a family history of gastric cancer; those with gastroesophageal reflux disease, which increases the risk of cardia cancer; and those with chronic atrophic gastritis, an important risk factor for cardia gastric cancer. Diabetes, obesity, psychosocial factors, and immune factors may also be associated with gastric cancer. For high-risk groups, upper gastrointestinal endoscopy is used for screening. Prevention includes reducing salt intake; eating less pickled, smoked, and fried foods, red meat, and processed meat; increasing intake of vegetables and fruit; chewing slowly; quitting smoking and limiting alcohol; paying attention to gastric diseases such as gastric intraepithelial neoplasia, chronic atrophic gastritis, gastric polyps, remnant stomach after surgery, hypertrophic gastritis, and gastric intestinal metaplasia; receiving timely treatment and regular re-examination; and promptly treating Helicobacter pylori infection.

Cancer screening and early diagnosis and treatment constitute secondary prevention of cancer, targeting high-risk groups with specific cancer screening. Primary prevention of cancer is the first line of defense in cancer control. Its core is to reduce the incidence of cancer at its source by changing unhealthy lifestyle habits, avoiding carcinogenic risk factors, and receiving preventive vaccines. This can effectively prevent about 45 percent of cancers. Therefore, several measures are recommended. First, strictly control tobacco use and stay away from tobacco hazards. Tobacco is a definite Group 1 carcinogen, closely related to lung cancer, esophageal cancer, bladder cancer, and many other cancers. People should actively quit smoking, avoid exposure to secondhand smoke and thirdhand smoke, reject new tobacco products such as e-cigarettes, and strictly implement tobacco control measures in public places to reduce environmental tobacco exposure. Second, stay away from carcinogenic pathogens and receive protective vaccines. Some viruses and bacteria are definite carcinogenic agents and require targeted prevention: receive HPV vaccines to prevent cervical cancer, anal cancer, and others; receive hepatitis B vaccines to reduce the risk of liver cancer; actively screen for and eradicate Helicobacter pylori to prevent gastric cancer; and avoid unsafe sexual practices and unsafe injections to reduce the risk of virus transmission.

Third, strictly limit alcohol consumption and avoid alcohol-related carcinogenesis. Alcohol is also a definite Group 1 carcinogen, and there is no safe level of alcohol consumption. It is recommended to avoid alcohol whenever possible; when drinking is unavoidable, strictly control the amount, and avoid drinking on an empty stomach, frequent binge drinking, and drinking spirits, so as to reduce alcohol-induced damage to the digestive tract and liver. Fourth, maintain a healthy weight and avoid obesity-related carcinogenesis. Studies show that overweight or obesity is associated with an increased risk of at least 13 cancers, such as breast cancer, colorectal cancer, liver cancer, and esophageal cancer. Obesity promotes cancer risk through hormonal imbalance, metabolic abnormalities, and other mechanisms. Body weight should be controlled within the normal range, with a BMI of 18.5 to 23.9, through diet and exercise, and abdominal obesity should be avoided to reduce the risk of metabolism-related cancers. Fifth, persist in moderate exercise to enhance immunity. It is recommended to engage in at least 150 minutes of moderate-intensity aerobic exercise per week, such as brisk walking, jogging, swimming, or cycling, or at least 75 minutes of vigorous-intensity exercise, combined with strength training twice a week. Regular exercise can reduce the risk of various cancers, including colorectal cancer and breast cancer, while improving metabolism and strengthening immunity.

Sixth, practice a healthy diet and build a strong dietary defense. Eat more fresh vegetables and fruit, whole grains, and legumes; reduce intake of red meat and processed meat; eat less pickled, barbecued, and fried foods; avoid high-salt, high-sugar, and high-fat diets; have regular meals; do not binge eat; and avoid eating very hot food or eating too quickly, so as to reduce damage to the esophageal mucosa. Seventh, reduce environmental and occupational carcinogenic exposure. Improve indoor air quality and avoid exposure to kitchen fumes, indoor formaldehyde, and coal combustion pollution; strengthen occupational protection and avoid long-term exposure to industrial carcinogens such as asbestos, benzene, and formaldehyde; protect against excessive ultraviolet radiation and avoid excessive sun exposure to reduce the risk of skin cancer; and promote breastfeeding to reduce the risk of breast cancer in women.