Cancer prevention 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.

Avoiding risk factors and increasing protective factors may help prevent 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.

Cancer prevention clinical trials are used to study ways to prevent cancer.

Cancer prevention clinical 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.

Skin cancer is a disease in which malignant (cancer) cells form in the tissues of the skin.

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:

• Squamous cells are the thin, flat cells that make up most of the epidermis.
• Basal cells are the round cells under the squamous cells.
• Melanocytes are found throughout the lower part of the epidermis. They make melanin, the pigment that gives skin its natural color. When skin is exposed to the sun, melanocytes make more pigment, causing the skin to tan, or darken.

The dermis contains blood and lymph vessels, hair follicles, and glands.

There are several types of 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.

Skin cancer is the most common cancer in the United States.

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 40 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.

Being exposed to ultraviolet radiation is a risk factor for skin 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.

• Risk factors for nonmelanoma skin cancer:
  • Being exposed to natural sunlight or artificial sunlight (such as from tanning beds) over long periods of time.
  • Having a fair complexion, which includes the following:
    • Fair skin that freckles and burns easily, does not tan, or tans poorly.
    • Blue or green or other light-colored eyes.
    • Red or blond hair.
  • Having actinic keratosis.
  • Past treatment with radiation.
  • Having a weakened immune system.
  • Being exposed to arsenic.
• Risk factors for melanoma skin cancer:
  • Having a fair complexion, which includes the following:
    • Fair skin that freckles and burns easily, does not tan, or tans poorly.
    • Blue or green or other light-colored eyes.
    • Red or blond hair.
  • Being exposed to natural sunlight or artificial sunlight (such as from tanning beds) over long periods of time.
  • Having a history of many blistering sunburns, especially as a child or teenager.
  • Having several large or many small moles.
  • Having a family history of unusual moles (atypical nevus syndrome).
  • Having a family or personal history of melanoma.
  • Being White.

Although having a fair complexion is a risk factor for nonmelanoma and melanoma skin cancer, people of all skin colors can get skin cancer.

It is not known if the following lower the risk of nonmelanoma skin cancer:

Sunscreen use and avoiding sun exposure

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 decreasethe 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:

• Use sunscreen that protects against UV radiation.
• Do not stay out in the sun for long periods of time, especially when the sun is at its strongest.
• Wear long sleeve shirts, long pants, sun hats, and sunglasses, when outdoors.

Chemopreventive agents

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:

Beta carotene

Studies of beta carotene (taken as a supplement in pills) have not shown that it prevents nonmelanoma skin cancer from forming or coming back.

Isotretinoin

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.

Selenium

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.

Celecoxib

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.

Alpha-difluoromethylornithine (DFMO)

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.

Nicotinamide (vitamin B3)

Studies have shown that nicotinamide (vitamin B3) helps prevent new actinic keratoses lesions from forming in people who had four or fewer actinic lesions before taking nicotinamide. More studies are needed to find out if nicotinamide prevents nonmelanoma skin cancer from forming or coming back.

It is not known if the following lower the risk of melanoma:

Sunscreen

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.

Counseling and protecting the skin from the sun

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.

The U.S. Preventive Services Task Force (USPSTF) has concluded there is not enough evidence to recommend for or against routine screening (total body examination by a doctor) to find skin cancers early. This recommendation is for people who do not have a history of skin cancer and who do not have any suspicious moles or other spots.

Checking your skin for moles regularly will help you find any suspicious changes. Be sure to check less visible areas of your skin like the soles of your feet. Tell your doctor about any unusual moles or changes in your skin. Also talk to your doctor if you are at increased risk of skin cancer.

Most skin cancers are caused by too much exposure to ultraviolet (UV) rays. UV rays come from the sun, tanning beds, and sunlamps. UV rays can damage skin cells.

To lower your risk of getting skin cancer, you can protect your skin from UV rays from the sun and from artificial sources like tanning beds and sunlamps.

Practice Sun Safety

Protection from UV rays is important all year, not just during the summer. UV rays can reach you on cloudy and cool days, and they reflect off of surfaces like water, cement, sand, and snow. In the continental United States, UV rays are strongest from 10 a.m. to 4 p.m. daylight saving time (9 a.m. to 3 p.m. standard time).

The UV Index forecasts the strength of UV rays each day. If the UV index is 3 or higher in your area, protect your skin from too much exposure to the sun. CDC recommends easy ways to protect your skin when the UV index is 3 or higher—

• Stay in the shade.
• Wear clothing that covers your arms and legs.
• Wear a hat with a wide brim to shade your face, head, ears, and neck.
• Wear sunglasses that wrap around and block both UVA and UVB rays.
• Use a broad spectrum sunscreen with a sun protection factor (SPF) of 15 or higher.

Avoid Indoor Tanning

Indoor tanning (using a tanning bed, booth, sunbed, or sunlamp to darken the skin) exposes users to high levels of UV rays. Over time, too much exposure to UV rays can cause skin cancers, cataracts, and cancers of the eye.

A tan does not indicate good health. When UV rays reach the skin’s inner layer, the skin makes more melanin. Melanin is the pigment that gives skin its color. It moves toward the outer layers of the skin and becomes visible as a tan. Any change in skin color after UV exposure (whether it is a tan or a burn) is a sign of injury, not health.

Indoor tanning—

• Exposes users to intense levels of UV rays, a known cause of cancer.
• Does not protect against sunburns. A “base tan” is actually a sign of skin damage.
• Can lead to serious injury. Indoor tanning accidents and burns send more than 3,000 people to the emergency room each year.

Spending time outside is a great way to be physically active, reduce stress, and get vitamin D. You can work and play outside without raising your skin cancer risk by protecting your skin from the sun.

Most skin cancers are caused by too much exposure to ultraviolet (UV) light. UV rays are an invisible kind of radiation that comes from the sun, tanning beds, and sunlamps. UV rays can damage skin cells.

Protection from UV rays is important all year, not just during the summer. UV rays can reach you on cloudy and cool days, and they reflect off of surfaces like water, cement, sand, and snow. In the continental United States, UV rays tend to be strongest from 10 a.m. to 4 p.m. daylight saving time (9 a.m. to 3 p.m. standard time).

The UV Index forecasts the strength of UV rays each day. If the UV index is 3 or higher in your area, protect your skin from too much exposure to the sun.

How to Protect Your Skin From the Sun

Shade

You can reduce your risk of sun damage and skin cancer by staying in the shade under an umbrella, tree, or other shelter. Your best bet to protect your skin is to use sunscreen or wear protective clothing when you’re outside—even when you’re in the shade.

Clothing

When possible, wear long-sleeved shirts and long pants and skirts, which can provide protection from UV rays. If wearing this type of clothing isn’t practical, try to wear a T-shirt or a beach cover-up. Clothes made from tightly woven fabric offer the best protection. A wet T-shirt offers much less UV protection than a dry one, and darker colors may offer more protection than lighter colors. Some clothing is certified under international standards as offering UV protection.

Hat

For the most protection, wear a hat that has a brim all the way around that shades your face, ears, and the back of your neck. A tightly woven fabric, such as canvas, works best to protect your skin from UV rays. Avoid straw hats with holes that let sunlight through. A darker hat may offer more UV protection.

If you wear a baseball cap, you should also protect your ears and the back of your neck by wearing clothing that covers those areas, using sunscreen, or staying in the shade.

Sunglasses

Sunglasses protect your eyes from UV rays and reduce the risk of cataracts. They also protect the tender skin around your eyes from sun exposure.

Sunglasses that block both UVA and UVB rays offer the best protection. Most sunglasses sold in the United States, regardless of cost, meet this standard. Wrap-around sunglasses work best because they block UV rays from sneaking in from the side.

Sunscreen

Put on broad spectrum sunscreen that blocks both UVA and UVB rays and has an SPF of 15 or higher before you go outside. Don’t forget to put a thick layer on all exposed skin. Get help for hard-to-reach places like your back. And remember, sunscreen works best when combined with other options.

Sunscreen is not recommended for babies who are 6 months old or younger. The U.S. Food and Drug Administration recommends keeping infants out of the sun during midday and using protective clothing if they have to be in the sun.

SPF. Sunscreens are assigned a sun protection factor (SPF), which is a number that rates how well they block UV rays. Higher numbers indicate more protection. You should use a broad spectrum sunscreen with SPF of 15 or higher.

Reapplication. Sunscreen wears off. Put it on again if you stay out in the sun for more than 2 hours and after swimming, sweating, or toweling off.

Expiration date. Check the sunscreen’s expiration date. Sunscreen without an expiration date has a shelf life of no more than 3 years. Its shelf life is shorter if it has been exposed to high temperatures.

Sun Safety Tips for Schools

Recess and other outdoor activities during the day can put students at risk if their skin isn’t protected from too much exposure to the sun. Teachers and school administrators can take steps to protect students from getting skin cancer later in life.

Increase Shade

• Provide shade structures or trees.
• Move outdoor activities to shaded areas.
• Plan for shade when developing or renovating school buildings, playgrounds, or athletic fields.

Promote Sun-Safe Behaviors

• Encourage students to wear hats, sunglasses, and sunscreen outdoors.
• Try to avoid scheduling outdoor activities when the sun is strongest.
• Provide breaks during outdoor activities so that students can reapply sunscreen and get water.

Use Proven Educational Programs

Proven skin cancer prevention interventions and educational programs are available for child care centers and schools.

Sun Safety Tips for Employers

The Occupational Safety and Health Act requires employers to minimize risk of harm to workers. Employers may be required to provide workers’ compensation to employees who get skin cancer because of sun exposure on the job.

Skin cancer can greatly reduce workers’ productivity. Every year, Americans lose more than $100 million in productivity because of restricted activity or absence from work due to skin cancer.

Providing sun protection for outdoor workers helps create a healthy and safe workplace. It can also increase productivity, which saves money.

Increase Sun Protection for Employees

• Encourage sun safety among your employees and provide sun protection when possible.
• Use tents, shelters, and cooling stations to provide shade at worksites.
• Schedule breaks in the shade and allow workers to reapply sunscreen throughout their shifts.
• Create work schedules that minimize sun exposure. For example, schedule outdoor tasks like mowing for early morning instead of noon, and rotate workers to reduce their UV exposure.

Add Sun Safety to Workplace Policies and Training

• Include sun-safety information in workplace wellness programs. The National Cancer Institute’s Evidence-Based Cancer Control Programs website lists sun safety programs for outdoor worksites.
• Teach outdoor workers about the risks of exposure to UV rays and the symptoms of overexposure.