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 is not known if the following lower the risk of melanoma:
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.
Cancer prevention clinical trials are used to study ways to prevent cancer.
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.
New ways to prevent skin cancer are being studied in clinical trials.
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 for clinical trials in NCI's PDQ Cancer Clinical Trials Registry for nonmelanoma skin cancer prevention trials and melanoma prevention trials that are now accepting patients.