The current situation and precise strategies of early screening for cancer: from limitation analysis to scientific prevention

Author: Senior Product Manager of UA Views：563

The global incidence rate of cancer continues to rise. According to the data of the International Agency for Research on Cancer (IARC) of the World Health Organization, in 2020, the number of new cancer cases worldwide will exceed 19.3 million, and the number of deaths will be nearly 10 million. Early screening, as a key means of reducing cancer mortality, has become a core issue in the field of public health.

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The global incidence of cancer continues to rise. According to data from the World Health Organization's International Agency for Research on Cancer (IARC), there were over 19.3 million new cancer cases and nearly 10 million cancer-related deaths worldwide in 2020. As a key means to reduce cancer mortality, early screening has become a core issue in the public health sector. However, there is a significant gap between the general health check-ups currently available and the public's expectations for cancer early screening. In clinical practice, there have been numerous cases where conventional check-ups failed to detect malignant tumors at an early stage. A thorough analysis of the root causes of this contradiction and the establishment of an evidence-based precise screening and prevention system are of great significance for improving cancer prevention and control efficiency.

I. Analysis of the Limitations of Conventional Physical Examinations in Cancer Early Screening

Conventional health check-ups, as a universal health assessment tool, are designed to detect chronic diseases such as hypertension and diabetes, as well as basic health issues, rather than specifically targeting the early detection of malignant tumors. Their limitations mainly manifest in three aspects:

Insufficient Specificity in Technical Means

Routine physical examination items (such as blood routine, basic biochemistry, and chest X-rays) lack the ability to specifically detect malignant tumors. Taking lung cancer as an example, chest X-rays have a detection rate of less than 20% for nodules smaller than 1 cm in diameter, which are typical of early-stage lung cancer. Gastrointestinal tumors such as gastric and esophageal cancer often have no specific symptoms in the early stages, and conventional examination items like abdominal ultrasound and Helicobacter pylori antibody testing cannot replace the intuitive diagnostic value of endoscopy. Clinical data shows that approximately 60% of early-stage liver cancers and 40% of early-stage gastric cancers are missed in conventional physical examinations, highlighting the lack of technical specificity.

Misunderstandings in the Clinical Application of Tumor Markers

Tumor markers (such as CEA, AFP, and PSA) are often regarded by the public as "cancer test strips," but their diagnostic value is actually limited by multiple factors. On one hand, non-malignant conditions such as inflammation and benign hyperplasia can lead to false positives (e.g., elevated AFP in hepatitis patients). On the other hand, approximately 30%-40% of patients with malignant tumors (such as poorly differentiated liver cancer and early-stage prostate cancer) may have normal tumor marker levels, resulting in false negatives. The American Society of Clinical Oncology (ASCO) clearly states that tumor markers can only be used as auxiliary diagnostic indicators and need to be comprehensively judged in combination with imaging and pathological examinations; they cannot be used as the basis for early screening alone.

Lack of Individualized Assessment Systems

The core of cancer early screening lies in "individualization," that is, formulating screening strategies based on an individual's risk stratification (such as family history, exposure history, and underlying diseases). Conventional physical examinations adopt a "one-size-fits-all" model and cannot identify high-risk groups. For example, a chest X-ray alone is clearly insufficient for smokers with a family history of lung cancer; while for young people without high-risk factors, excessive use of high-end examinations such as PET-CT will increase radiation risks and medical burdens. The lack of a family doctor system leads to discontinuous individual health records, making it difficult to achieve long-term dynamic risk assessment, which is also an important reason for the gap in cancer early screening efficiency between China and European and American countries.

II. Precise Screening Strategies for Major Malignant Tumors

Based on evidence-based medical evidence, international authoritative institutions (such as the American Cancer Society and the Oncology Branch of the Chinese Medical Association) have formulated individualized screening guidelines for high-incidence cancers, with the core being "targeting high-risk groups + applying specific technologies."

Lung Cancer

Screening Technology: Low-dose computed tomography (LDCT) is currently the only screening method proven to reduce lung cancer mortality. Compared with chest X-rays, LDCT increases the detection rate of early-stage lung cancer by 4-5 times, with a radiation dose only 1/5-1/10 of conventional CT.

Definition of High-Risk Groups: Individuals aged ≥40 years with any of the following risk factors: smoking ≥20 pack-years (daily smoking amount × smoking years, e.g., 1 pack per day for 20 years) or quitting smoking for <15 years; long-term passive smoking (exposure in family or work environment); occupational exposure to carcinogens such as asbestos, radon, and uranium; family history of lung cancer or personal history of malignant tumors; combined chronic obstructive pulmonary disease or diffuse pulmonary fibrosis.

Screening Frequency: Annual LDCT for high-risk groups; routine screening is not recommended for non-high-risk groups.

Liver Cancer

Screening Technology: The combination of alpha-fetoprotein (AFP) and abdominal ultrasound is the "gold standard" for early liver cancer screening. AFP has a diagnostic specificity of approximately 70%-80% for hepatocellular carcinoma, while ultrasound can detect small lesions <1 cm in diameter. The combination of the two can increase the early diagnosis rate to over 90%. It should be noted that AFP subtypes (such as AFP-L3) have higher specificity for early liver cancer (up to 95%) and can be used as supplementary detection indicators.

Definition of High-Risk Groups: Males aged ≥35 years and females aged ≥45 years with risk factors such as HBV/HCV infection, cirrhosis (of any cause), family history of liver cancer, or drug-induced liver injury.

Screening Frequency: Combined AFP + ultrasound examination every 6 months. For those with abnormal AFP or nodules found by ultrasound, further enhanced CT/MRI is recommended for confirmation.

Breast Cancer

Screening Technology: Complementary application of mammography (X-ray) and ultrasound. Mammography has significant advantages in detecting microcalcifications (a typical manifestation of early intraductal carcinoma), while ultrasound is more sensitive in identifying lesions in dense breasts (common in Asian women); magnetic resonance imaging (MRI) is used for extremely high-risk groups (such as BRCA mutation carriers).

Definition of High-Risk Groups: Nulliparous women or primiparous women aged ≥35 years; women with menarche ≤12 years or menopause ≥55 years; first-degree relatives (parents, children, siblings) with breast cancer before the age of 50; previous breast biopsy confirming severe atypical hyperplasia; history of chest radiotherapy for ≥10 years.

Screening Frequency: For the general population, mammography every 1-2 years for 40-49 years old, and annual mammography for those over 50 years old; for high-risk groups, annual MRI + ultrasound starting from 20 years old, and additional mammography starting from 35 years old.

Colorectal Cancer

Screening Technology: Colonoscopy is the gold standard for early colorectal cancer screening, which can directly observe mucosal lesions and remove adenomatous polyps (precancerous lesions), thereby blocking the carcinogenesis process. Fecal occult blood test (FOBT) can be used as a preliminary screening method, and positive cases require further colonoscopy.

Definition of High-Risk Groups: People over 40 years old with persistent anorectal symptoms (such as hematochezia, changes in defecation habits); first-degree relatives with a history of colorectal cancer; history of adenomatous polyps; inflammatory bowel diseases such as ulcerative colitis; family members of hereditary syndromes (such as familial adenomatous polyposis).

Screening Frequency: For the general population, colonoscopy every 10 years or annual FOBT for 45-75 years old; for high-risk groups, annual colonoscopy (such as after adenoma resection) or every 1-2 years (for family members of hereditary syndromes).

Gastric Cancer

Screening Technology: Gastroscopy can directly observe gastric mucosal lesions and take biopsies, with an accuracy rate of over 95% for diagnosing early gastric cancer, significantly better than X-ray barium meal, CT, and other examinations.

Definition of High-Risk Groups: Individuals with any of the following conditions: people over 60 years old; moderate to severe atrophic gastritis; chronic gastric ulcer; gastric polyps; gastric mucosal giant fold sign; residual stomach after benign disease surgery (10 years after surgery); residual stomach after gastric cancer surgery (6-12 months after surgery); Helicobacter pylori infection; clear family history of gastric or esophageal cancer; pernicious anemia.

Screening Frequency: Regular gastroscopy according to the doctor's advice.

Prostate Cancer

Screening Technology: Serum prostate-specific antigen (PSA) testing is the main method, but its specificity is limited (about 70%) and needs to be combined with digital rectal examination (DRE).

Definition of High-Risk Groups: Men over 50 years old; men over 45 years old with a family history of prostate cancer; men over 40 years old with PSA >1ng/mL.

Screening Frequency: PSA + DRE every 2 years for high-risk groups; prostate biopsy is recommended for those with PSA >4ng/mL.

Cervical Cancer

Screening Technology: Liquid-based cytology (TCT) combined with high-risk HPV testing. Persistent HPV infection (especially types 16/18) is the main cause of cervical cancer, and the combination of the two can improve the early detection rate.

Definition of High-Risk Groups: Individuals with multiple sexual partners, early sexual activity (<16 years old); persistent positive HPV; immunocompromised; history of cervical intraepithelial neoplasia.

Screening Frequency: TCT every 3 years for 21-29 years old; TCT + HPV every 5 years or TCT every 3 years for 30-65 years old; screening can be stopped for those over 65 years old without high-risk factors.

III. Primary Prevention of Cancer: Evidence-Based Modifiable Factors

The World Health Organization points out that about 40% of cancers can be prevented through primary prevention (etiological prevention). Based on epidemiological and mechanistic studies, the following modifiable factors have clear evidence in cancer prevention:

Hydration Status and Urinary System Health

Epidemiological studies have shown that drinking ≥2000mL of water per day can reduce the risk of bladder cancer (relative risk RR=0.62, 95% CI: 0.51-0.75). The mechanism is that increasing urine output can reduce the contact time between carcinogens in urine (such as nitrites and aromatic amines) and the bladder mucosa, reducing chronic irritation. It is recommended that adults drink 1500-2000mL of water per day, mainly boiled water and light tea, and avoid sugary drinks.

Psychosocial Factors and Immune Regulation

Chronic psychological stress inhibits immune function through the hypothalamic-pituitary-adrenal axis (HPA), reducing NK cell activity and cytokine secretion (such as IL-2 and IFN-γ), and promoting tumor progression. Prospective cohort studies have shown that the incidence of breast cancer is increased by 37% in patients with severe depression (RR=1.37, P<0.01), and the prognosis is worse. Improving mental state through social support and cognitive behavioral therapy can enhance immune surveillance function. This "psychology-immunity-tumor" axis provides a new perspective for cancer prevention.

Core Role of Tobacco Control

Tobacco smoke contains more than 70 carcinogens (such as benzopyrene and nitrosamines) and is associated with 17 types of cancer. People who smoke ≥20 cigarettes per day have a 25-fold higher risk of lung cancer than non-smokers, and the risks of bladder cancer and gastric cancer are increased by 3-fold and 2-fold, respectively. Even light smoking (1-9 cigarettes per day) still results in a 3-fold higher risk of lung cancer than non-smokers. The risk decreases over time after quitting smoking, and the risk of lung cancer in those who have quit smoking for 10 years drops to 30%-50% of that in smokers. Therefore, "quitting smoking at any time is beneficial, and the earlier the better" is an evidence-based conclusion.

Regular Exercise and Energy Balance

The World Cancer Research Fund (WCRF) has confirmed that moderate-intensity exercise ≥150 minutes per week (such as brisk walking and swimming) can reduce the risk of colorectal cancer (RR=0.76) and breast cancer (RR=0.81). Exercise works by regulating insulin resistance, reducing inflammatory factors (such as TNF-α and IL-6), and improving intestinal flora. "Walking" is recommended as the basic exercise, combined with resistance training (such as dumbbells) to maintain muscle mass and optimize metabolism.

Optimization of Dietary Patterns

A high-salt diet (>6g per day) increases the risk of gastric cancer by 2-fold by damaging the gastric mucosal barrier and promoting Helicobacter pylori colonization; processed meats (such as sausages and ham) contain nitrites, which are metabolized into nitrosamines and associated with colorectal cancer (RR=1.18). It is recommended to adopt a "Mediterranean diet" pattern: increase the intake of whole grains, vegetables, and fruits (rich in dietary fiber and antioxidants), control the intake of red meat (<500g per week) and salt, and avoid moldy food (aflatoxin is associated with liver cancer).

Moderate Vitamin D Acquisition

Vitamin D inhibits tumor cell proliferation by regulating the cell cycle (such as p21 and p53 genes), and its deficiency is associated with an increased risk of colorectal cancer (RR=1.31) and breast cancer (RR=1.24). Moderate sun exposure (10:00-15:00 daily, exposing the face and forearms for 10-20 minutes) can promote skin synthesis of vitamin D. In winter, supplements (400-600IU per day) can be used to maintain levels.

Weight Management and Metabolic Health

Obesity (BMI≥28kg/m²) is associated with 13 types of cancer through mechanisms such as insulin resistance and excessive estrogen (adipose tissue is a peripheral synthesis site for estrogen). Waist circumference is a more sensitive indicator than BMI. Men with waist circumference ≥85cm and women with waist circumference ≥80cm have a significantly increased risk of colorectal cancer and pancreatic cancer. Maintaining a healthy weight (BMI 18.5-23.9kg/m²) through diet and exercise is a key part of cancer prevention.

Adherence to Individualized Screening

Data from the National Cancer Institute (NCI) shows that standardized screening can reduce colorectal cancer mortality by 53% and breast cancer mortality by 39%. However, the participation rate of cancer screening in China is less than 20%, with the main obstacles including insufficient awareness ("no screening without symptoms"), fear of examinations (such as discomfort from colonoscopy), and economic factors. Establishing a "risk stratification-precision recommendation-follow-up management" screening system, combined with community medical promotion, is the key to improving participation.

Conclusion

Cancer prevention and control need to shift from "passive discovery" to "active prevention" and upgrade from "universal physical examination" to "precision screening." Only by understanding the limitations of conventional physical examinations, mastering the high-risk factors and screening technologies of different cancers, and combining primary prevention measures such as diet, exercise, and psychology, can a comprehensive cancer prevention and control network be built. In the future, with the development of technologies such as liquid biopsy (such as circulating tumor DNA) and artificial intelligence imaging diagnosis, cancer early screening will become more precise and convenient. However, the current evidence-based strategies have been proven effective - the key lies in "knowing and doing it," transforming scientific knowledge into healthy behaviors.

This article is reviewed and published by the technical expert team of UA

Disclaimer: This article partially utilizes artificial intelligence assistance in its creation. If any content involves copyright or intellectual property issues, please let us know and we promise to verify and remove it as soon as possible.

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