Cancer Prevention: What the Evidence Says

• A. Excessive sun exposure
• B. Tobacco use ✓
• C. Air pollution
• D. Processed foods

Why: Tobacco use is the leading preventable cause of cancer worldwide, linked to many cancer types including lung, mouth, throat, bladder, pancreas, and kidney cancers.

• A. A genetic mutation inherited from a parent
• B. A risk factor that a person can change through lifestyle or behavior ✓
• C. A risk factor that only affects older adults
• D. A risk factor identified only in laboratory studies

Why: Modifiable risk factors, such as smoking, diet, physical activity, alcohol use, and sun exposure, are those individuals can change to reduce their cancer risk.

• A. Physical inactivity
• B. Obesity
• C. Age ✓
• D. Alcohol consumption

Why: Age is a non-modifiable risk factor. Cancer risk generally rises with age because of accumulated cell damage over time, while the other options can be changed by behavior.

• A. Probably carcinogenic to humans
• B. Possibly carcinogenic to humans
• C. Carcinogenic to humans (Group 1) ✓
• D. Not carcinogenic to humans

Why: IARC classifies alcohol consumption as Group 1, meaning it is carcinogenic to humans, with links to cancers of the mouth, throat, esophagus, liver, colon, rectum, and breast.

• A. Taking vitamin D supplements daily
• B. Using sunscreen, wearing protective clothing, and avoiding peak sun hours ✓
• C. Getting a tan before a vacation to build protection
• D. Using tanning beds regularly to build a base tan

Why: Combining sunscreen, protective clothing, shade, and avoiding peak UV hours is the evidence-based approach to reducing skin cancer risk. Tanning beds and tanning in general increase risk.

• A. Excessive sun exposure
• B. Tobacco use ✓
• C. Obesity
• D. Air pollution

Why: Tobacco use is the single largest preventable cause of cancer death worldwide, responsible for a substantial share of cancer deaths across many populations, and it is linked to cancers of the lung, mouth, throat, esophagus, bladder, pancreas, kidney, and others.

• A. Prostate cancer
• B. Thyroid cancer
• C. Lung cancer ✓
• D. Skin melanoma

Why: Lung cancer has the strongest and most well-established association with cigarette smoking, with smoking responsible for the large majority of lung cancer cases in many countries.

• A. Nicotine
• B. Carbon monoxide
• C. Polycyclic aromatic hydrocarbons and tobacco-specific nitrosamines ✓
• D. Ammonia

Why: Tobacco smoke contains many carcinogens, including polycyclic aromatic hydrocarbons and tobacco-specific nitrosamines, which damage DNA and promote mutations. Nicotine itself is addictive but is not considered a primary carcinogen.

• A. It stays the same permanently
• B. It increases sharply
• C. It gradually decreases over time ✓
• D. It decreases only after 50 years

Why: Cancer risk declines gradually after quitting smoking, with the reduction continuing over many years. Quitting at any age provides benefit, and the earlier a person quits, the greater the protection.

• A. Smoking a cigar yourself
• B. Breathing smoke from someone else's cigarette in a home or workplace ✓
• C. Using e-cigarettes in a private room
• D. Chewing smokeless tobacco

Why: Secondhand smoke is the smoke exhaled by smokers together with smoke released from the burning end of a cigarette. Breathing it in is a recognized cause of lung cancer in nonsmokers, which is why smoke-free policies are an important prevention strategy.

• A. High consumption of processed meat ✓
• B. Eating whole grains daily
• C. Drinking green tea regularly
• D. Eating a moderate amount of nuts

Why: The International Agency for Research on Cancer classifies processed meat as a Group 1 carcinogen, based on sufficient evidence linking it to colorectal cancer. Higher intake is associated with increased risk, so limiting processed meats such as bacon, ham, and sausages is a recommended prevention strategy.

• A. Being overweight or obese increases the risk of several cancers, including breast, colorectal, and endometrial cancer ✓
• B. Body weight has no measurable relationship with cancer risk
• C. Only very underweight individuals face increased cancer risk
• D. Weight affects only lung cancer risk

Why: Excess body fat is linked to higher risk of at least 13 cancer types, including breast (postmenopausal), colorectal, endometrial, kidney, and liver cancers. Fat tissue alters hormone levels such as estrogen and insulin, and promotes chronic low-grade inflammation, all of which can influence cancer development.

• A. Only heavy binge drinking carries any risk
• B. Any level of alcohol consumption increases cancer risk, with risk rising as intake increases ✓
• C. Red wine in moderation prevents all cancers
• D. Alcohol increases risk only for liver cancer

Why: Alcohol is classified as a Group 1 carcinogen. It is linked to cancers of the mouth, throat, esophagus, liver, colon, rectum, and breast. Risk generally increases with the amount consumed, and no level of drinking is considered completely free of risk.

• A. Fiber increases colorectal cancer risk by irritating the colon
• B. Fiber has no effect on colorectal cancer risk
• C. Higher fiber intake from whole grains, fruits, and vegetables is associated with lower colorectal cancer risk ✓
• D. Only supplements, not food sources of fiber, reduce risk

Why: Multiple large studies and reviews have found that diets rich in fiber from whole grains, vegetables, fruits, and legumes are associated with a lower risk of colorectal cancer. Fiber may help by speeding transit time, diluting potential carcinogens, and feeding beneficial gut bacteria that produce protective compounds.

• A. Eating fruits and vegetables reliably prevents all cancers
• B. Fruits and vegetables are a healthy part of a diet and are associated with reduced risk of some cancers, particularly those of the mouth, esophagus, and stomach, but they are not a guaranteed preventive measure ✓
• C. Fruits and vegetables have been shown to cause cancer in humans
• D. Only organic produce provides any cancer protection

Why: Evidence consistently links higher fruit and vegetable intake with lower risk of certain cancers such as those of the mouth, esophagus, and stomach. However, the effect is modest, and no single food guarantees protection. Eating a varied, plant-rich diet is a sensible part of an overall prevention strategy rather than a complete solution.

• A. Physical activity has no measurable effect on colon cancer risk.
• B. Higher levels of physical activity are associated with a lower risk of colon cancer. ✓
• C. Physical activity increases colon cancer risk when performed at moderate intensity.
• D. Only vigorous exercise lasting more than three hours per day affects colon cancer risk.

Why: Large cohort studies and meta-analyses consistently show that people who are more physically active have a lower risk of colon cancer, and this association is among the best-established for physical activity and cancer.

• A. 30 minutes per week
• B. 60 minutes per week
• C. 150 minutes per week ✓
• D. 500 minutes per week

Why: The WHO and many national guidelines recommend at least 150 minutes of moderate-intensity aerobic activity per week for adults, which is also associated with reduced cancer risk.

• A. By increasing circulating insulin and growth factor levels
• B. By reducing insulin resistance and lowering chronic inflammation ✓
• C. By raising estrogen levels in all adults
• D. By thickening the lining of the colon

Why: Regular activity improves insulin sensitivity, reduces circulating insulin and insulin-like growth factors, lowers chronic inflammation, and helps regulate sex hormones and immune function, all of which are linked to cancer development.

• A. Only skin cancer
• B. Breast cancer, particularly postmenopausal breast cancer ✓
• C. Thyroid cancer only
• D. No cancer types have been linked to inactivity

Why: Several cancers, including colon, breast (especially postmenopausal), endometrial, and kidney cancers, show associations with physical inactivity, and postmenopausal breast cancer is among the most consistently studied.

• A. Survivors should avoid all physical activity to prevent recurrence.
• B. Regular physical activity is generally safe and may improve quality of life and reduce some recurrence risk for many survivors. ✓
• C. Physical activity only helps survivors who have never received treatment.
• D. Survivors should only perform activity at maximum intensity to see benefits.

Why: Evidence supports that most cancer survivors can safely engage in regular physical activity, which is associated with better quality of life, reduced fatigue, and in some cancers, lower recurrence and mortality, though individualized guidance from a clinician is advisable.

• A. Only liver cancer
• B. Cancers of the mouth, pharynx, larynx, esophagus, liver, colorectum, and breast ✓
• C. Only lung cancer
• D. No cancers; the link is limited to cardiovascular disease

Why: IARC Group 1 classification recognizes alcohol as a cause of several cancers, including oral cavity, pharynx, larynx, esophagus, liver, colorectum, and female breast cancer. The link is not limited to a single organ.

• A. Alcohol directly damages DNA with no metabolic step involved
• B. Alcohol is metabolized into acetaldehyde, a toxic compound that can damage DNA and impair its repair ✓
• C. Alcohol raises body temperature enough to cause cell mutations
• D. Alcohol lowers immune function only in people over age 80

Why: Ethanol is converted to acetaldehyde, a known carcinogen, which can form DNA adducts and cross-links and interfere with DNA repair. Alcohol can also act through hormone changes such as increased estrogen levels.

• A. Excess body weight has no established relationship with cancer
• B. Excess body weight is linked to an increased risk of several cancers, including endometrial, kidney, and postmenopausal breast cancer ✓
• C. Excess body weight only increases the risk of skin cancer
• D. Only very underweight people face increased cancer risk

Why: Overweight and obesity are established risk factors for at least 13 cancer types, including endometrial, kidney, liver, esophageal adenocarcinoma, and postmenopausal breast cancer, largely through insulin, insulin-like growth factor, and estrogen pathways.

• A. Drinking more alcohol on weekends to balance intake
• B. Avoiding alcohol altogether, or drinking as little as possible, since there is no completely safe level of intake ✓
• C. Switching from beer to wine, since wine is cancer-free
• D. Drinking only on an empty stomach

Why: No level of alcohol consumption is considered completely free of cancer risk, and risk rises with the amount consumed. Reducing or avoiding alcohol is the most direct recommendation. Beverage type does not eliminate the risk.

• A. Eating large portions of energy-dense foods to build reserves
• B. Staying physically active, eating a diet rich in vegetables, fruits, whole grains, and legumes, and limiting sugary drinks and processed meat ✓
• C. Eliminating all carbohydrates from the diet
• D. Relying on supplements instead of diet and exercise

Why: Cancer prevention guidance recommends regular physical activity, a diet based on plant foods, limiting sugary drinks and processed meats, and avoiding weight gain across adulthood. Supplements are not a substitute for these habits.

• A. Epstein-Barr virus (EBV)
• B. Human papillomavirus (HPV) ✓
• C. Hepatitis B virus (HBV)
• D. Herpes simplex virus type 2 (HSV-2)

Why: Persistent infection with high-risk types of human papillomavirus (HPV), especially HPV-16 and HPV-18, causes nearly all cases of cervical cancer. HPV vaccination and cervical screening are both effective prevention strategies.

• A. Hepatitis A virus
• B. Hepatitis C virus only
• C. Hepatitis B virus ✓
• D. Hepatitis E virus

Why: Chronic hepatitis B infection can lead to cirrhosis and hepatocellular carcinoma. Hepatitis B vaccination in infancy has substantially reduced liver cancer rates in vaccinated populations. Hepatitis A does not cause chronic infection and is not linked to liver cancer.

• A. It cures existing liver tumors
• B. It prevents chronic hepatitis B infection, reducing the risk of liver cancer later ✓
• C. It boosts the body's immunity against all cancers
• D. It removes the virus from infected liver cells

Why: By preventing the initial hepatitis B infection, the vaccine stops the chronic inflammation and liver damage that can progress to cirrhosis and liver cancer. It is a preventive measure, not a treatment for established disease.

• A. Helicobacter pylori ✓
• B. Streptococcus pneumoniae
• C. Escherichia coli
• D. Staphylococcus aureus

Why: Helicobacter pylori causes chronic gastritis and is a major risk factor for stomach cancer. It is classified as a Group 1 carcinogen. Eradicating H. pylori with antibiotics can reduce stomach cancer risk, especially when done before precancerous changes develop.

• A. The vaccine only works in people who have never been exposed to HPV
• B. The vaccine is less effective after exposure, since most people are infected with HPV at some point ✓
• C. Younger people have stronger immune systems that the vaccine requires
• D. The vaccine causes permanent immunity only if given in childhood

Why: HPV is extremely common, and most sexually active people acquire at least one type during their lives. Vaccinating before first exposure gives the greatest protection, since the vaccine prevents infection rather than clearing existing infection, though it can still offer benefit to some older adults.

• A. To cure cancer once symptoms appear
• B. To detect cancer or precancerous changes early, when treatment is often more effective ✓
• C. To confirm whether a person has a specific genetic mutation
• D. To replace the need for a physical examination by a doctor

Why: Screening tests are used on people without symptoms to find cancer or precancerous lesions early, when they are often smaller, less advanced, and more treatable. Screening does not cure cancer by itself.

• A. Chest X-ray
• B. Mammogram
• C. Colonoscopy or stool-based testing such as fecal immunochemical test (FIT) ✓
• D. Prostate-specific antigen (PSA) blood test

Why: Colorectal cancer screening commonly uses colonoscopy, which can also remove precancerous polyps, or stool-based tests like FIT. Mammograms screen for breast cancer, PSA tests relate to prostate cancer, and chest X-rays are not a standard screening tool for colorectal cancer.

• A. They always detect every cancer that is present
• B. They can produce false positives, leading to additional testing, and false negatives, where cancer is missed ✓
• C. They are only useful for people over 90 years old
• D. They eliminate the risk of developing cancer

Why: No screening test is perfect. False positives can cause anxiety and unnecessary follow-up procedures, while false negatives can give a false sense of reassurance. Screening also cannot guarantee that cancer will never develop.

• A. To measure hormone levels in the blood
• B. To detect abnormal cervical cells or high-risk human papillomavirus infection that can lead to cervical cancer ✓
• C. To check for lung cancer in smokers
• D. To identify skin cancer on the cervix

Why: Cervical screening looks for abnormal cells (Pap test) or high-risk HPV, the virus that causes nearly all cervical cancers. Finding these early allows monitoring or treatment before invasive cancer develops.

• A. Everyone of that age must be tested immediately regardless of risk
• B. Screening is generally recommended to begin at that age for average-risk people, based on evidence of benefit versus harm at that stage of life ✓
• C. Testing before that age is always harmful
• D. The age only applies to people who already have symptoms

Why: Age-based screening recommendations reflect evidence about when the benefits of screening outweigh potential harms for average-risk individuals. People with higher risk, such as those with a family history, may need to start earlier, and clinicians tailor advice accordingly.