What does cancer prevention mean?

Cancer prevention is action taken to lower the chance of getting cancer. By preventing cancer, the number of new cases is lowered, which can reduce the burden of cancer and lower the number of deaths from it.

Cancer is not a single disease but a group of related diseases. Many things in our genes, our lifestyle, and the environment around us may increase or decrease our risk of getting cancer.

Scientists study many ways to help prevent cancer, including:

• Avoiding or controlling things known to cause cancer
• Making changes in diet and lifestyle
• Finding precancerous conditions early
• Using medicines to lower risk (chemoprevention)
• Risk-reducing surgery

Those five lines cover very different kinds of action. Here is what each one looks like in practice.

Avoiding known causes

This is where the largest single lever sits. The National Cancer Institute ties about 30% of all US cancer deaths to smoking.

NCI names other risk factors too. Obesity is linked to several cancers: breast cancer after menopause, colon and rectal cancer, endometrial cancer, and cancers of the esophagus, kidney, and pancreas. Alcohol is tied to cancers of the mouth, esophagus, and breast. Being inactive raises risk. So does radiation, from sunlight and from sources such as radon and medical imaging.

Some causes are infections. NCI names HPV, hepatitis B and C, Epstein-Barr virus, and Helicobacter pylori.

Diet and lifestyle

Changes here move risk, though usually less than quitting tobacco does. NCI notes that a diet high in fat may raise the risk of colon and rectal cancer. It also notes that people who move less carry more risk.

Finding precancerous conditions early

This one is easy to overlook, and it is prevention in the strictest sense. A colonoscopy that removes a polyp has prevented a cancer, not found one. The same goes for treating abnormal cervical cells picked up by screening.

Vaccines belong here too. Two vaccines approved by the FDA stop cancer by stopping the infection behind it. Those are the hepatitis B vaccine and the HPV vaccine.

Medicines that lower risk

Chemoprevention means taking a drug to lower cancer risk in someone who does not have cancer. NCI gives real examples. Tamoxifen and raloxifene lower breast cancer risk. Finasteride has been used for prostate cancer. COX-2 inhibitors were studied for colon and breast cancer, but heart risks limited that work.

These are not for everyone. They suit people whose risk is high enough to justify the trade-off.

Risk-reducing surgery

This is the most drastic option. It is reserved for people with a strong inherited risk or family history. NCI lists removal of the breasts, ovaries, fallopian tubes, colon, stomach, or thyroid among the operations used this way.

What prevention cannot do

Not every risk factor can be avoided, so prevention lowers the chances of cancer but cannot guarantee it.

That is worth stating plainly, in both directions. People who do everything right still get cancer, and that is not a personal failure. People who did not still may not, because chance is a real part of this.

Prevention is a bet on probability, played over decades. It is worth making. It is not a promise.

Your healthcare team can suggest steps that make sense for you.