Cancer prevention

The majority of cancer cases are due to the accumulation of environmental pollution being inherited as epigenetic damage and most of these environmental factors are controllable lifestyle choices. Greater than a reported 75% of cancer deaths could be prevented by avoiding risk factors including: tobacco, overweight / obesity, an insufficient diet, physical inactivity, alcohol, sexually transmitted infections, and air pollution. Not all environmental causes are controllable, such as naturally occurring background radiation, and other cases of cancer are caused through hereditary genetic disorders. Current genetic engineering techniques under development may serve as preventive measures in the future. Future preventive screening measures can be additionally improved by minimizing invasiveness and increasing specificity by taking individual biological makeup into account, also known as "population-based personalized cancer screening."

While anyone can get cancer, age is one of the biggest factors that increases the risk of cancer: 3 out of 4 cancers are found in people aged 55 or older.

Risk reduction

Dietary

An average 35% of human cancer mortality is attributed to the diet of the individual. Studies have linked excessive consumption of red or processed meat to an increased risk of breast cancer, colon cancer, and pancreatic cancer, a phenomenon which could be due to the presence of carcinogens in meats cooked at high temperatures. One review found increased risk of breast cancer to be associated with a higher intake of red and processed meats, eggs, refined sugars, alcohol, and saturated fats.

Dietary recommendations for reducing cancer risk typically include an emphasis on vegetables, fruit, whole grains, and fish, and an avoidance of processed and red meat (beef, pork, lamb), animal fats, and refined carbohydrates. The World Cancer Research Fund recommends a diet rich in fruits and vegetables to reduce the risk of cancer. A diet rich in foods of plant origin, including non-starchy fruits and vegetables, non-starchy roots and tubers, and whole grains, may have protective effects against cancer.

Consumption of coffee is associated with a reduced risk of liver cancer and endometrial cancer. High coffee intake was shown to be related to a lower risk of melanoma and oral cancer. However, a higher risk of childhood acute lymphocytic leukemia and bladder cancer was associated with higher coffee intake. Substituting processed foods, such as biscuits, cakes or white bread – which are high in fat, sugars and refined starches – with a plant-based diet may reduce the risk of cancer. In some cases, plant-based diets have shown to be inversely associated with overall cancer risk.

While many dietary recommendations have been proposed to reduce the risk of cancer, the evidence to support them is not definitive. Factors that may increase risk are alcohol consumption, and a diet low in fruits and vegetables and high in red meat. A 2014 meta-analysis did not find a relationship between consuming fruits and vegetables and reduced cancer risk.

Physical activity

Research shows that regular physical activity may help to reduce cancer up to 30%, with up to 300 minutes per week of moderate to vigorous intensity of physical activity recommended.

Possible mechanisms by which physical activity may reduce cancer risk include lowering levels of estrogen and insulin, reducing inflammation, and strengthening the immune system. Regular physical activity activates tumor suppressor genes like p53, reduces cell proliferation to prevent tumor development, increases apoptosis or cell death in tumor tissue, and can reduce obesity-related cancer risk, as obesity is associated with increased risk of many types of cancer.

Medication and supplements

In the general population, NSAIDs reduce the risk of colorectal cancer; however, due to the cardiovascular and gastrointestinal side effects, they cause overall harm when used to lower cancer risk. Aspirin use after a cancer diagnosis is associated with about a 20% reduction in cancer mortality. COX-2 inhibitors may decrease the rate of polyp formation in people with familial adenomatous polyposis however are associated with the same adverse effects as NSAIDs. Daily use of tamoxifen or raloxifene has been demonstrated to reduce the risk of developing breast cancer in high-risk women. The benefit verses harm for 5-alpha-reductase inhibitor such as finasteride is not clear.

Vitamins supplements have not been found to be effective at reducing overall cancer risk, although observational studies consistently show that low blood levels of vitamin D are correlated with increased cancer risk. Whether this relationship is causal and vitamin D supplementation is protective is not determined. Beta-carotene supplementation has been found to increase lung cancer rates in those who are at high risk. Folic acid supplementation has not been found effective in preventing colon cancer and may increase colon polyps. A 2018 systematic review concluded that selenium has no beneficial effect in reducing the risk of cancer based on high quality evidence.

Avoidance of carcinogens

The United States National Toxicology Program identified the chemical substances as known human carcinogens in its 15th Report on Carcinogens in 2022. Simply because a substance has been designated as a carcinogen, however, does not mean that the substance will necessarily cause cancer. Many factors influence whether a person exposed to a carcinogen will develop cancer, including the amount and duration of the exposure and the individual's genetic background.

Updated evaluations by the International Agency for Research on Cancer support the carcinogenicity of asbestos and benzene, while also guiding the assessment of emerging substances in consumer products. A 2023 meta-analysis found that exposure to certain compounds suspected of endocrine disruption, including p,p′-DDT (and its metabolite p,p′-DDE) and several polychlorinated biphenyl variants, was associated with increased risk of breast cancer.

The International Agency for Research on Cancer classifies known, suspected or potential carcinogens into the following categories: Group 1 carcinogens, where sufficient evidence exists to support carcinogenicity in humans, Group 2A for probable carcinogens, Group 2B for possible carcinogens and group 3 for agents, chemical mixtures or exposure events not classifiable as either carcinogens or non-carcinogens due to inadequate evidence in humans or non-human animals. Group 4 is for non-carcinogens where strong evidence exists to support a lack of carcinogenicity.

Genetic and epigenetic factors

Genetic factors play a significant role in cancer risk, adding to the influence of modifiable environmental factors. Specific gene polymorphisms are associated with increased cancer risk. For instance, variations in the vitamin D receptor (VDR) gene are associated with elevated risks of both breast and ovarian cancers, suggesting that impaired vitamin D signaling may contribute to carcinogenesis. Similarly, inherited variations in the enzymes that contribute to the metabolism of carcinogens have been linked with an increased risk of colorectal cancer, demonstrating how genetic differences can affect the capacity of the body to break down cancer-causing substances. In addition to these inherited factors, environmental exposures can also alter gene regulation through epigenetic modifications. A systematic review on epigenetics, microbiota, and breast cancer revealed that factors like maternal diet and stress may alter epigenetic markers and impact the development and progression of breast cancer. Research on gene-environment interactions in colorectal cancer identified that lifestyle factors – such as the intake of processed meats, alcohol consumption, and the use of aspirin – affect cancer risk in individuals of specific genetic backgrounds, with aspirin's protective effects varying according to genetic makeup.

Vaccination

Anti-cancer vaccines can be preventive or be used as therapeutic treatment. All such vaccines incite adaptive immunity by enhancing cytotoxic T lymphocyte (CTL) recognition and activity against tumor-associated or tumor-specific antigens (TAA and TSAs).

Vaccines have been developed that prevent infection by some carcinogenic viruses. Human papillomavirus vaccine (Gardasil and Cervarix) decreases the risk of developing cervical cancer. The hepatitis B vaccine prevents infection with hepatitis B virus and thus decreases the risk of liver cancer. The administration of human papillomavirus and hepatitis B vaccinations is recommended when resources allow.

Some cancer vaccines are usually immunoglobulin-based and target antigens specific to cancer or abnormal human cells. These vaccines may be given to treat cancer during the progression of disease to boost the immune system's ability to recognize and attack cancer antigens as foreign entities. Antibodies for cancer cell vaccines may be taken from the patient's own body (autologous vaccine) or from another patient (allogeneic vaccine). Several autologous vaccines, such as Oncophage for kidney cancer and Vitespen for a variety of cancers, have either been released or are undergoing clinical trial. FDA-approved vaccines, such as Sipuleucel-T for metastasizing prostate cancer or Nivolumab for melanoma and lung cancer can act either by targeting over-expressed or mutated proteins or by temporarily inhibiting immune checkpoints to boost immune activity.

Screening

Screening procedures, commonly sought for more prevalent cancers, such as colon, breast, and cervical, have greatly improved in the past few decades from advances in biomarker identification and detection. Early detection of pancreatic cancer biomarkers was accomplished using a SERS-based immunoassay approach. A SERS-based multiplex protein biomarker detection platform in a microfluidic chip can be used to detect several protein biomarkers to predict the type of disease and critical biomarkers and increase the chance of diagnosis between diseases with similar biomarkers (e.g. pancreatic cancer, ovarian cancer, and pancreatitis).

To improve the chances of detecting cancer early, all eligible people should take advantage of cancer screening services. However, overall uptake of cancer screening among the general population is not widespread, especially among disadvantaged groups (e.g. those with low income, mental illnesses, or are from different ethnic groups) who face different barriers that lead to lower attendance rates. Research indicates that these screening barriers are influenced by both individual circumstances and area-level factors. A systematic review of lung cancer screenings found that feelings of fear, anxiety, and negative attitudes toward the screening process can discourage individuals from participating. Additionally, a review examining clinical and psychosocial aspects associated with breast, cervical, and colorectal cancer screening found that factors like personal beliefs, social support, and effective communication with healthcare providers are associated with screening attendance.

Beyond the personal and psychosocial factors, broader socioeconomic elements also impact screening participation rates. Women with lower income are 20% more likely to not participate in breast cancer screening, with lower education increasing the likelihood of skipping screening by 18%. Immigrant women have nearly triple the odds of non-participation, and individuals living further away from their assigned screening facility, as well as those with a male family doctor, are also less likely to participate in screening. Rural communities often face significant transportation barriers, with long travel distances and limited access to public transportation further reducing access to screening services. In addition, in these rural areas, the uneven distribution of healthcare providers and limited availability of telehealth services can exacerbate these disparities, reducing access to specialized cancer screening.

Health literacy

Health literacy – the ability to navigate and use health care information – is an important factor in cancer prevention. Studies show that individuals with better health literacy are more likely to follow through with cancer screening programs for breast, cervical, and colorectal cancers. Some intervention programs aimed at improving health literacy are shown to not only boost understanding of health information but also address psychosocial aspects, such as patient communication and decision conflict. These interventions include patient decision aids, multimedia educational tools, and clinician communication training, which are linked to improvements in patient knowledge, risk perception, and comfortability with screening processes. Enhancing health literacy by addressing patients' informational and emotional needs may help to reduce disparities in cancer prevention.

Cervical cancer

Cervical cancer is usually screened through in vitro examination of the cells of the cervix (e.g. Pap smear), colposcopy, or direct inspection of the cervix (after application of dilute acetic acid), or testing for HPV, the oncogenic virus that is the necessary cause of cervical cancer. Screening is recommended for women over 21 years, initially women between 21 and 29 years old are encouraged to receive Pap smear screens every three years, and those over 29 every five years. For women older than the age of 65 and with no history of cervical cancer or abnormality, and with an appropriate precedence of negative Pap test results may cease regular screening.

Still, adherence to recommended screening plans depends on age and may be linked to "educational level, culture, psychosocial issues, and marital status," further emphasizing the importance of addressing these challenges in regards to cancer screening.

Colorectal cancer

Colorectal cancer is most often screened with the fecal occult blood test (FOBT). Variants of this test include guaiac-based FOBT (gFOBT), the fecal immunochemical test (FIT), and stool DNA testing (sDNA). Further testing includes flexible sigmoidoscopy (FS), total colonoscopy (TC), or computed tomography (CT) scans if a total colonoscopy is non-ideal. The recommended age at which to begin and continue screening is 50–75 years. However, this is highly dependent on medical history and exposure to risk factors for colorectal cancer. Effective screening has been shown to reduce the incidence of colorectal cancer by 33% and colorectal cancer mortality by 43%.

Breast cancer

The estimated number of new breast cancer cases in the US in 2018 is predicted to be more than 1.7 million, with more than six hundred thousand deaths. Factors such as breast size, reduced physical activity, obesity and overweight status, infertility and never having had children, hormone replacement therapy (HRT), and genetics are risk factors for breast cancer. Mammograms are widely used to screen for breast cancer, and are recommended for women 50–74 years of age by the US Preventive Services Task Force (USPSTF). However, the USPSTF does not recommend mammograms for women 40–49 years old due to the possibility of overdiagnosis.