Nearly Half of Cancer Cases Could Be Avoided

Four in 10 cancer cases are caused by modifiable risk factors such as cigarette smoking or being overweight, according to a new study.

In 2024, about two million people in the United States will be diagnosed with cancer, a debilitating condition that is also the leading cause of death worldwide. Only 5–10% of all cancer cases are attributed to genetics, while the rest are rooted in the environment and lifestyle.

A new study published in CA: A Cancer Journal for Clinicians suggests that about 40% of all cancer cases are caused by modifiable risk factors, such as cigarette smoking, excess body weight, alcohol consumption, and viruses like human papillomavirus, among others.

In the study, researchers used nationally representative data on cancer incidence and mortality and the prevalence of risk factors. The data allowed them to estimate the proportion and number of cancer cases and deaths attributable to potentially modifiable risk factors overall, excluding non-melanoma skin cancers, and for 30 individual cancer types.

Excess body weight was associated with the second largest proportion of cancer cases attributable to risk factors, accounting for 7.6% of cases. About 40% of Americans have obesity, putting them at a higher risk of colorectal, endometrial, ovarian, and liver cancers, among others.

Alcohol consumption was attributed to 5.4% of cancer cases caused by modifiable risk factors, followed by UV radiation exposure (4.6%), and physical inactivity (3.1%).

Alcohol is classified as a Group 1 carcinogen by the International Agency for Research on Cancer, along with asbestos, radiation, and tobacco. There is no safe amount of alcohol — it increases the risk of at least seven types of cancer at any consumption.

Exposure to UV rays, whether from sunlight or tanning devices, is a risk factor for all types of skin cancer and is especially dangerous for people with a weakened immune system, as well as a personal or family history of skin cancer.

Physical activity not only reduces the risk of cancer but has other major health benefits. People who exercise are less likely to develop cardiovascular disease, type 2 diabetes, and hypertension.

Risk factors differ in their impact

For 19 of 30 evaluated cancer types in the study, the effect of modifiable risk factors exceeded 50%. The impact ranged from 100% for cervical cancer and Kaposi sarcoma to 4.9% for ovarian cancer.

Some 92.2% of all melanomas of the skin and cancers of the anus (94.2%), larynx (89.9%), lung and bronchus (lung; 88.2%), pharynx (87.4%), trachea (85.6%), esophagus (85.4%), and oral cavity (83.7%) were attributable to evaluated risk factors.

The study also looked at dietary risk factors, such as consumption of red and processed meat, as well as low consumption of fruits and vegetables, dietary fiber, and dietary calcium. A poor diet is among the main contributors to colorectal cancer in Americans younger than 50 years old.

How can I protect myself from cancer?

Knowing the potential causes of cancer allows you to reduce the risk of developing it. Consider the following lifestyle changes:

• Quit cigarette smoking. Don’t start if you are a non-smoker.
• Avoid alcohol — there is no safe amount.
• Exercise regularly — aim for at least 150 minutes of physical activity a week.
• Eat a diet rich in fruits, vegetables, and whole grains.
• Limit the consumption of red and processed meat.
• Always wear sunscreen.
• Consider getting an HPV vaccine.
• Undergo pap smear and other screening tests regularly.

Lifestyle changes can help significantly reduce the risk of developing cancer but do not offer 100% protection. If you’re experiencing any new symptoms, discuss them with your healthcare provider.