Source: National Cancer Institute Research, www.cancer.gov
Cancerprevention is action taken to lower the chance of getting cancer. By preventing cancer, the number of new cases of cancer in a group or population is lowered. Hopefully, this will lower the number of deaths caused by cancer.
To prevent new cancers from starting, scientists look at risk factors and protective factors. Anything that increases your chance of developing cancer is called a cancer risk factor; anything that decreases your chance of developing cancer is called a cancer protective factor.
Some risk factors for cancer can be avoided, but many cannot. For example, both smoking and inheriting certain genes are risk factors for some types of cancer, but only smoking can be avoided. Regular exercise and a healthy diet may be protective factors for some types of cancer. Avoiding risk factors and increasing protective factors may lower your risk but it does not mean that you will not get cancer.
Different ways to prevent cancer are being studied, including:
The skin is the body’s largest organ. It protects against heat, sunlight, injury, and infection. Skin also helps control body temperature and stores water, fat, and vitamin D. The skin has several layers, but the two main layers are the epidermis (upper or outer layer) and the dermis (lower or inner layer).
The epidermis is made up of 3 kinds of cells:
The dermis contains blood and lymph vessels, hair follicles, and glands.
See the following PDQ summaries for more information about skin cancer:
The most common types of skin cancer are squamous cell carcinoma, which forms in the squamous cells and basal cell carcinoma, which forms in the basal cells. Squamous cell carcinoma and basal cell carcinoma are also called nonmelanoma skin cancers. Melanoma, which forms in the melanocytes, is a less common type of skin cancer that grows and spreads quickly.
Skin cancer can occur anywhere on the body, but it is most common in areas exposed to sunlight, such as the face, neck, hands, and arms.
Basal cell carcinoma and squamous cell carcinoma are the most common types of skin cancer in the United States. The number of new cases of nonmelanoma skin cancer appears to be increasing every year. These nonmelanoma skin cancers can usually be cured.
The number of new cases of melanoma has been increasing for at least 30 years. Melanoma is more likely to spread to nearby tissues and other parts of the body and can be harder to cure. Finding and treating melanoma skin cancer early may help prevent death from melanoma.
Avoiding cancerrisk factors may help prevent certain cancers. Risk factors include smoking, being overweight, and not getting enough exercise. Increasing protective factors such as quitting smoking, eating a healthy diet, and exercising may also help prevent some cancers. Talk to your doctor or other health care professional about how you might lower your risk of cancer.
Some studies suggest that being exposed to ultraviolet (UV) radiation and the sensitivity of a person’s skin to UV radiation are risk factors for skin cancer. UV radiation is the name for the invisible rays that are part of the energy that comes from the sun. Sunlamps and tanning beds also give off UV radiation.
Risk factors for nonmelanoma and melanoma cancers are not the same.
It is not known if nonmelanoma skin cancer risk is decreased by staying out of the sun, using sunscreens, or wearing protective clothing when outdoors. This is because not enough studies have been done to prove this.
Sunscreen may help decrease the amount of UV radiation to the skin. One study found that wearing sunscreen can help prevent actinic keratoses, scaly patches of skin that sometimes become squamous cell carcinoma.
The harms of using sunscreen are likely to be small and include allergic reactions to skin creams and lower levels of vitamin D made in the skin because of less sun exposure.
It is also possible that when a person uses sunscreen to avoid sunburn they may spend too much time in the sun and be exposed to harmful UV radiation.
Although protecting the skin and eyes from the sun has not been proven to lower the chance of getting skin cancer, skin experts suggest the following:
Chemoprevention is the use of drugs, vitamins, or other agents to try to reduce the risk of cancer. The following chemopreventive agents have been studied to find whether they lower the risk of nonmelanoma skin cancer:
Studies of beta carotene (taken as a supplement in pills) have not shown that it prevents nonmelanoma skin cancer from forming or coming back.
High doses of isotretinoin have been shown to prevent new skin cancers in patients with xeroderma pigmentosum. However, isotretinoin has not been shown to prevent nonmelanoma skin cancers from coming back in patients previously treated for nonmelanoma skin cancers. Treatment with isotretinoin can cause serious side effects.
Studies have shown that selenium (taken in brewer's yeast tablets) does not lower the risk of basal cell carcinoma, and may increase the risk of squamous cell carcinoma.
A study of celecoxib in patients with actinic keratosis and a history of nonmelanoma skin cancer found those who took celecoxib had slightly lower rates of recurrent nonmelanoma skin cancers. Celecoxib may have serious side effects on the heart and blood vessels.
A study of alpha-difluoromethylornithine (DFMO) in patients with a history of nonmelanoma skin cancer showed that those who took DFMO had lower rates of nonmelanoma skin cancers coming back than those who took a placebo. DFMO may cause hearing loss which is usually temporary.
It has not been proven that using sunscreen to prevent sunburn can protect against melanoma caused by UV radiation. Other risk factors such as having skin that burns easily, having a large number of benign moles, or having atypical nevi may also play a role in whether melanoma forms.
It is not known if people who receive counseling or information about avoiding sun exposure make changes in their behavior to protect their skin from the sun.
Cancer preventionclinical trials are used to study ways to lower the risk of developing certain types of cancer. Some cancer prevention trials are conducted with healthy people who have not had cancer but who have an increased risk for cancer. Other prevention trials are conducted with people who have had cancer and are trying to prevent another cancer of the same type or to lower their chance of developing a new type of cancer. Other trials are done with healthy volunteers who are not known to have any risk factors for cancer.
The purpose of some cancer prevention clinical trials is to find out whether actions people take can prevent cancer. These may include eating fruits and vegetables, exercising, quitting smoking, or taking certain medicines, vitamins, minerals, or food supplements.
Clinical trials are taking place in many parts of the country. Information about clinical trials can be found in the Clinical Trials section of the NCI Web site. Check NCI's list of cancer clinical trials for nonmelanoma skin cancer prevention trials and melanoma prevention trials that are now accepting patients.