Effectiveness of Available Interventions
Preventive strategies include reducing sun exposure (e.g., by wearing protective clothing and using sunscreen regularly), avoiding sunlamps and tanning equipment, and practicing skin self-examination. There is little direct evidence, however, that any of these interventions reduce skin cancer morbidity or mortality.
Reducing Sun Exposure
Avoiding direct sunlight by staying indoors or in the shade or by wearing protective clothing is the most effective measure for reducing exposure to ultraviolet light, but there are no randomized trials of sun avoidance to prevent skin cancer. In numerous observational studies, increased sun exposure in childhood and adolescence is associated with increased risk for non-melanoma skin cancer, which usually occurs in sun-exposed areas such as the face.
Recent studies provide a more complex picture of the relationship between sun exposure and melanoma, however. While melanoma incidence is higher in regions near the equator where ultraviolet exposure is most intense, melanoma often occurs in areas of the body not exposed to the sun. In observational studies, intermittent or intense sun exposure was associated with increased risk for melanoma; chronic exposure was associated with lower risk, as was the ability to tan.
Sunlamp and Tanning Bed Avoidance
Six of 19 case-control studies found a positive association between use of sun lamps and melanoma risk, but most did not adjust for recreational sun exposure or for the dosage and timing of sunlamp exposure. Among 9 studies that examined the duration, frequency, or timing of sunlamp or tanning bed exposure, 4 found a positive association, particularly if the dose of exposure was high and if it caused burning.
Sunscreen Use
Daily sunscreen use on the hands and face reduced the total incidence of squamous cell cancer in a randomized trial of 1,621 residents in Australia (rate ratio [RR] 0.61, 95% confidence interval [CI] 0.46-0.81). Sunscreen had no effect on basal cell cancer. Based on this trial, 140 people would need to use sunscreen daily for 4.5 years to prevent 1 case of squamous cell cancer. An earlier randomized trial demonstrated that sunscreen use reduced solar keratoses, precursors of squamous cell cancers. There are no direct data about the effect of sunscreen on melanoma incidence. An unblinded randomized trial showed children at high risk for skin cancers who used sunscreen developed fewer nevi than those who did not. Several epidemiologic studies have found higher risk for melanoma among users of sunscreens than among non-users. A recent meta-analysis of population-based case-control studies found no effect of sunscreen use on risk for melanoma. The conflicting results may reflect the fact that sunscreen use is more common among fair-skinned persons, who are at higher risk for melanoma, than it is among darker-skinned persons; or, this finding may reflect the fact that sunscreen use could be harmful if it encourages longer stays in the sun without protecting completely against cancer-causing radiation.
Skin Self-Examination
The only evidence for the effectiveness of skin self-examination comes from a single case-control study. After adjustment for other risk factors, skin self-examination was associated with lower incidence of melanoma (odds ratio [OR] 0.66, 95% CI 0.44-0.99) and lower mortality from melanoma (OR 0.37, 95% CI 0.16-0.84), although the definition of "self-examination" was limited. This study did not provide sufficient evidence that skin self-examination would reduce the incidence of melanoma or improve outcomes of melanoma.
Effectiveness of Counseling
Community and worksite educational interventions have demonstrated significantly increased use of skin protection measures, such as wearing hats and long-sleeve shirts and staying in the shade; however, evidence addressing the effectiveness of clinician counseling to prevent skin cancer is extremely limited. Most studies of counseling have examined intermediate outcomes such as knowledge and attitudes rather than changes in behavior. In a recent survey, 60% of pediatricians said that they usually or always counsel patients about skin protection, but advice to use sunscreen is more common than advice about wearing protective clothing or avoiding the midday sun.
Simple reminders and instructional materials for clinicians can overcome some of the barriers to regular counseling. A randomized trial of a community-based intervention involving 10 towns in New Hampshire suggests that office-based counseling by physicians may be an effective component of a multi-modal program to promote skin protection. The proportion of children with some sun protection increased in the intervention towns (from 78% to 87%) but not in control communities (P = 0.029). More parents reported receiving some sun protection information from a clinician in the intervention towns. However, most of the change was due to increased sunscreen use rather than to reduced sun exposure.
Subgroups Most Likely to Benefit:
UV exposure increases the risk for skin cancer among people with all skin types, but especially fair-skinned people. Those who sunburn readily and tan poorly, namely those with red or blond hair and fair skin that freckles or burns easily, are at highest risk for developing skin cancer and would benefit most from sun protection behaviors. The incidence of
melanoma among whites is 20 times higher than it is among blacks; the
incidence of melanoma among whites is about 4 times higher than it is among Hispanics.