To prevent cancer, pay attention to these 9 influencing factors! Expert interpretation is here

April 15-21, 2024 is the 30th National Cancer Prevention and Treatment Publicity Week . The theme of this year's publicity week is " Comprehensive measures, scientific cancer prevention ", and sub-topics such as "cancer prevention and treatment, early screening and early diagnosis", "weight management, start from me", and "core knowledge, you and I know". In order to help expand the popularization of cancer prevention and control science, popularize anti-cancer health knowledge, and comprehensively enhance the awareness of cancer prevention and control in the whole society, Kangxun.com specially invited Professor Huang Yubei of Tianjin Medical University Cancer Hospital to interpret the situation of cancer prevention and control in China, core knowledge of cancer prevention and early screening, etc.

Expert Profile

Professor Huang Yubei, Tianjin Medical University Cancer Hospital, PhD in Public Health, Associate Researcher, Master Supervisor

Researcher, Tumor Epidemiology and Biostatistics Laboratory, Tianjin Medical University Cancer Hospital

Standing Committee Member of the Cancer Screening and Early Diagnosis and Treatment Professional Committee of the Chinese Anti-Cancer Association

Standing Committee Member of the Third Translational Medicine Committee of Beijing Breast Disease Prevention and Treatment Society

The third level talents of Tianjin "131" innovative talents training project

The third batch of young innovative talents of Tianjin Medical University Cancer Hospital

He has presided over one National Natural Science Foundation project, one Tianjin Natural Science Foundation project, and one Tianjin Municipal Health Commission fund project, and participated in two national key R&D projects, two national science and technology support projects, and more than ten national natural and provincial and ministerial projects.

He won one International Union Against Cancer Technical Scholarship, participated in winning one special prize in Tianjin Science and Technology Progress Award, one first prize and one second prize in the China Anti-Cancer Association Science and Technology Award, and one national patent.

He has published more than 80 articles, including 25 SCI articles as the first author or corresponding author.

Reviewer for 25 Chinese and English journals including BMJ, BMJ Global Health, and Lancet Regional Health.

1. Cancer in my country shows a prevalence trend of "three highs and one low"

CA Cancer J Clin, a journal under the American Cancer Society, is one of the authoritative journals in the field of international oncology. Its published global cancer statistics report shows that in 2022, there will be 19.97 million new cases of cancer worldwide, of which nearly 4.82 million will be in my country, accounting for about 24% of the world's new cases. During the same period, there were about 9.74 million cancer deaths worldwide, and nearly 2.57 million cancer deaths in my country, accounting for about 27% of the world's deaths. Statistics show that the number of cases of the top five cancers in my country accounts for about 58% of all cancers, and the number of deaths from the top five cancers accounts for about 67% of all cancers.

From the above data, if the top five cancers with the highest number of cases can be effectively prevented and controlled, the cancer disease burden can be reduced by nearly 60%. However, the reality is that from 2000 to 2018, the incidence of most cancers in my country increased significantly, except for esophageal cancer, gastric cancer and liver cancer. Fortunately, from 2003 to 2015, the prognosis of most cancers in my country has improved significantly, and the overall 5-year survival rate has increased from 30.9% in 2003 to 40.5% in 2012. However, compared with the United States (the overall 5-year survival rate of cancer is 69.3%), except for gastric cancer and esophageal cancer, the 5-year survival rate of most cancers in my country is still far behind.

In addition, cancer imposes a heavy disease burden on Chinese residents. According to the survey, in my country, one out of every two cancer patients borrows money to see a doctor; one out of every ten cancer patients has to give up some treatment methods due to lack of money. The proportion of patients who gave up treatment due to financial difficulties was chemotherapy (38.0%), surgical treatment (25.7%), targeted therapy (11.2%), radiotherapy (5.0%), traditional Chinese medicine treatment (3.9%), and hormone therapy (2.2%). Nearly half of cancer survivors experienced financial difficulties, about 67% of patients borrowed 10,000-49,999 yuan, and 18% of patients borrowed more than 50,000 yuan.

Overall, cancer in China presents a grim situation of "three highs and one low" , namely high incidence (about 4 million new cases per year, 8 people/min), high mortality (about 2.4 million deaths per year, 5 people/min), high economic burden (total national health expenditure exceeds 5.4 trillion), and low survival rate (the overall 5-year survival rate is about 40.5%).

2. Scientific cancer prevention and understanding of core knowledge

Under the combined effects of host factors (genetics, epigenetics, microbial biomass, age, gender, metabolic status, inflammatory status, and immune function), environmental factors (food contamination, viral infection, radiation, environmental carcinogens, etc.), and diet/lifestyle factors (nutrients, energy intake, phytochemicals, alcohol, physical exercise, smoking, etc.), normal epithelial cells transform into precancerous lesions and further develop invasive cancers. A series of molecular events will change during this process.

The core thing we need to focus on is that host factors are factors that cannot be changed, while environmental factors and diet/lifestyle factors are factors that can be changed.

1. Age and Cancer

One study showed that the lifetime cumulative risk of cancer for men and women in Zhejiang Province, my country is 26.6% and 23.2%, respectively. Another study showed that the lifetime cumulative risk of cancer for men and women in the United States is 40.9% and 39.1%, respectively. The risk of cancer increases with age.

2. Genetic factors and cancer

As of August 2023, nearly 650 tumor genome-wide association studies have reported nearly 9,000 genetic susceptibility loci (low-penetrance common variants) worldwide, which can explain 10% to 30% of cancer heritability. In 2020, a study sequenced 28,076 tumor samples from 66 types of cancer and found a total of 568 cancer driver genes. Driver gene mutations (high-penetrance rare mutations, such as P53 and BRCA1, etc.) will bring a greater risk of cancer.

What counts as a family history of cancer?

In order to avoid the generalization of the concept of cancer family history and the panic caused by it, the "Guidelines for Integrated Diagnosis and Treatment of Cancer in China (CACA)" gives a clear definition of cancer family history, namely, two or more first- or second-degree relatives are diagnosed with the same cancer .

3. Modifiable factors and cancer

A study showed that in 2019, the global cancer burden attributable to modifiable risk factors was 42.0% (48% for men and 34% for women), with the top three factors being smoking (33.9% for men and 10.7% for women), drinking (7.4% for men and 2.3% for women), and high body mass index (BMI, 4.3% for men and 4.7% for women). The attributable risk ratios varied widely among provinces, with the lowest being Shanghai (35.2%) and the highest being Heilongjiang (52.9%).

(1) Diet and cancer

"Diet, Nutrition, Physical Activity and Cancer: A Global Perspective Summary" points out that "fast food" or other processed foods high in fat and sugar increase the risk of obesity-related cancers by increasing weight, while vegetables and fruits protect cells in the body from carcinogenic damage by providing vitamins, minerals and plant compounds.

(2) Smoking and cancer

As early as 1950, tobacco was identified as a lung cancer carcinogen. Subsequently, a large amount of evidence showed that smoking can increase the risk of cancer in 17 parts other than lung cancer (kidney, ureter, bladder, ovary, cervix, nasal cavity, nasopharynx, oral cavity, oropharynx, hypopharynx, larynx, esophagus, stomach, liver, pancreas, large intestine, etc.). In addition, relevant studies conducted by the International Agency for Research on Cancer have confirmed that passive smoking is also carcinogenic.

(3) Overweight, obesity and cancer

Being overweight or obese increases the risk of 15 types of cancer (esophageal adenocarcinoma, postmenopausal breast cancer, stomach cancer, pancreatic cancer, kidney cancer, colorectal cancer, prostate cancer, multiple myeloma, certain types of head and neck cancer, thyroid cancer, liver cancer, gallbladder cancer, ovarian cancer, endometrial cancer, meningioma). The main reasons for the increased risk of cancer include: chronic low-level inflammation, temporary "storage" of hormones, and increased diabetes-related cancers. On the contrary, physical exercise can reduce the risk of 9 tumors (esophageal adenocarcinoma, postmenopausal breast cancer, stomach cancer, kidney cancer, colorectal cancer, liver cancer, endometrial cancer, lung cancer, bladder cancer).

The obesity-attributable proportion of the global cancer burden is higher in women than in men (mortality: 4.7% in women vs. 4.3% in men; morbidity: 5.4% in women vs. 1.9% in men).

How to determine overweight and obesity?

Expert Consensus on Obesity Prevention and Treatment in Chinese Residents (2022) BMI Criteria for Chinese Population:

Underweight (BMI < 18.5).

Normal BMI is 18.5-23.9.

Overweight BMI 24.0～27.9.

Obesity BMI ≥ 28.0.

(4) Alcohol consumption and cancer

Drinking alcohol clearly increases the risk of six types of cancer, including certain types of head and neck cancer, esophageal cancer, breast cancer, colorectal cancer, liver cancer and stomach cancer. The main reason why drinking alcohol increases the risk of cancer is that ethanol is metabolized into acetaldehyde in the body, which is a clear carcinogen. In addition, drinking alcohol affects the absorption of nutrients such as vitamins, which can also increase the risk of cancer.

(5) Infection and cancer

Studies have shown that in 2018, there were approximately 2.2 million cases of cancer attributed to infection worldwide (Table 1).

Table 1 Global cancer cases attributable to infection

The population attributable fraction of cancer deaths among people aged 20 years and above in China in 2014 was attributed to the four pathogens (Table 2).

Table 2 Attributable fractions of cancer deaths among people aged 20 and above in my country

(6) Environmental pollution and cancer

In 2017, there were 179,300 lung cancer deaths in my country caused by air pollution, of which 141,500 were caused by particulate matter pollution and 37,800 were attributable to indoor air pollution caused by solid fuels.

(7) Radiation exposure and cancer

In 2022, nearly 5% of new cancers in adults over 30 in the United States can be attributed to exposure to UV radiation. The risk exceeds the risk of cancer from an unhealthy diet, infections, and a sedentary lifestyle.

Small amounts of UV radiation play a vital role in the production of vitamin D, but too much can be harmful. In 2020, overexposure to UV radiation caused an estimated 1.2 million cases of non-melanoma skin cancer and 325,000 cases of cutaneous melanoma, as well as 64,000 premature deaths from non-melanoma and 57,000 from cutaneous melanoma worldwide.

What is the risk of medical radiation from radiological examinations?

Compared with clear carcinogenic factors (such as smoking), the risk of medical radiation from routine examinations is extremely low. Physicians and engineers are committed to reducing medical radiation doses. When an examination is necessary, refusing the examination is far greater than the risk of radiation.

(8) Female factors and cancer

Breast cancer is a hormone-dependent malignant tumor. Any factor that may increase female hormone exposure may increase the risk of breast cancer, including early age of menarche, late age of menopause, oral contraceptives, hormone replacement therapy, infertility/late childbearing, abortion, and no breastfeeding/short breastfeeding duration.

At present, the physiological reproductive characteristics of Chinese women are progressing at an unprecedented trend, mainly manifested in the continuous decrease in the age of menarche, the continuous postponement of the age of menopause, the significant decrease in the average number of births, the obvious delay in the age of first childbirth, the extension of the interval between two childbirths, and the significant decrease in the average breastfeeding time. These changes will lead to a serious trend in the incidence of breast cancer in the future, which is worrying.

(9) Breast characteristics and cancer

Compared with loose breasts, women with dense breasts have a higher risk of breast cancer. The proportion of dense breasts in Chinese women aged 45 to 65 is 49.2%, which is higher than the proportion of dense breasts in white Americans (48.7%). It is worth noting that being postmenopausal and having more live births are negatively correlated with dense breasts, while a history of benign breast disease and a late first childbirth age are positively correlated with dense breasts.

3. Cancer Prevention Recommendations

The World Health Organization clearly pointed out that about one-third of cancers can be prevented by reducing carcinogenic factors, which is applicable to the entire population. In terms of cancer prevention, the World Cancer Research Fund and the American Institute for Cancer Research have given 10 suggestions. Maintain a healthy weight.

· Actively participate in exercise.

Eat more whole grains, legumes, vegetables, and fruits.

Limit fast food and processed foods that are high in fat and sugar.

Eat less red and processed meat.

Drink less sugary drinks.

Drink less alcohol, or better yet, don’t drink alcohol.

Do not use nutritional supplements to prevent cancer.

If possible, mothers should breastfeed.

Cancer patients should follow the above suggestions if possible.

The European Cancer Prevention Guidelines add the following recommendations: do not smoke or use any type of tobacco, maintain a smoke-free environment and avoid second-hand smoke; participate in vaccination programs for hepatitis B virus and human papillomavirus; participate in cancer screening programs for colorectal cancer, female breast cancer and cervical cancer.

4. Early screening and diagnosis reduce the burden of cancer

In addition, the World Health Organization has also clearly pointed out that 1/3 of cancers can be detected early. Currently, there is a large amount of high-level randomized controlled study evidence that early screening can reduce common cancer deaths by 20% to 48% (Table 3). Table 3 Foreign screening evidence

At present, my country has included some cancers into the cancer screening public health program supported by the central government (Table 4).

Table 4 Domestic screening items

Recommended methods in my country's common cancer screening guidelines and the latest global evidence.

1. Lung cancer

The "Chinese Lung Cancer Screening Standard (T/CPMA013-2020)" recommends low-dose spiral CT. Studies have shown that a one-time low-dose CT lung screening for people aged 40 to 74 in my country can effectively reduce lung cancer deaths by 31.0% and all-cause deaths by 32%.

2. Breast cancer

The Chinese Women's Breast Cancer Screening Standard (T/CPMA014-2020) recommends breast ultrasound or mammography. British data show that starting at age 40 or 41, annual mammography for women before age 50 can reduce breast cancer deaths by 25%.

3. Colorectal cancer

The "Guidelines for Colorectal Cancer Screening, Early Diagnosis and Treatment in China (2020, Beijing)" recommends a screening regimen that combines colonoscopy (every 5 to 10 years) with fecal occult blood test (every year).

A practical randomized controlled study of people aged 55 to 64 in four European countries showed that full colonoscopy screening can effectively reduce the incidence of colorectal cancer by 18%, but did not significantly reduce the mortality rate.

4. Gastric cancer

The "Expert Consensus on the Screening Process for Early Gastric Cancer in China" recommends three screening items of gastric function (serum pepsinogen I/II, gastrin-17 levels, Helicobacter pylori antibodies) and gastroscopy.

Studies have shown that a one-time endoscopic screening for people aged 40 to 69 in high-risk areas of my country can effectively reduce the incidence of upper gastrointestinal tumors by 23% and the mortality rate by 57%.

5. Liver cancer

The "Guidelines for Liver Cancer Screening in the Chinese Population (2022, Beijing)" recommends abdominal ultrasound, alpha-fetoprotein testing, and magnetic resonance imaging.

For people who are positive for hepatitis B virus surface antigen, annual ultrasound combined with alpha-fetoprotein examination can increase the survival rate by 1.5 to 2 times compared with liver cancer patients who have not been screened.

Compared with European and American countries, cancer in China has three highs and one low: high incidence, high mortality, high economic burden, and low survival rate . Smoking, drinking, obesity, dietary factors, lack of physical activity, pathogen infection, air pollution, and heredity are the main risk factors for cancer. Except for heredity, all of them are modifiable risk factors.

Primary prevention measures such as quitting smoking, promoting a healthy lifestyle, and avoiding infection, as well as secondary prevention measures such as screening high-risk groups and early diagnosis and treatment can effectively reduce the disease burden of cancer.