Sunscreen and Melanoma: Is Our Prevention Message Correct

¶ … Sunscreen and melanoma: Is our prevention message correct

The idea that sunscreen is an effective weapon against melanoma has become so commonly cited it has become a cliche: not only do primary care providers make the recommendation to wear sunscreen with a SPF over 15 -- even magazines and popular memes underline this advice. However, according to Planta (2011), evidence-based research does not support the idea that sunscreen protects against cutaneous malignant melanoma (CMM). In fact, although rates of sunscreen use have increased in recent years, the rates of this particularly deadly form of melanoma have also continued to rise at a rate of 3% per annum (Planta 2011). There is also a correlation between the use of sunblock and the likelihood of developing sunburns, which leads to an elevated risk of developing melanoma. Even children whose parents applied sunblock more regularly, according to one Swedish study of children ages 5-7, had higher rather than lower rates of skin cancer. The U.S. Environmental Protection Agency concluded "there is no evidence that sunscreens protect you from malignant melanoma" (Planta 2011).

It should be noted that studies are contradictory regarding sunscreen efficacy overall in terms of preventing skin cancer of all varieties: according to some studies, sunblock may be useful in reducing the risks of squamous cell carcinoma but not basal cell carcinoma. While "although there is convincing evidence that nonmelanoma skin cancer is related to cumulative sun exposure, there is less evidence of that association with CMM. If CMM were related to cumulative sun exposure, one would expect that outdoor workers would have a greater incidence of CMM than indoor workers. However, that is not the case" (Planta 2011). In fact, CCM is increasing most rapidly amongst individuals who spend the bulk of their hours indoors and who receive three to nine times less solar UV radiation than those who spend most of their time outside. "Furthermore, there is a higher incidence of CMM among whites living in northern states such Delaware, Vermont, and New Hampshire (>30 per 100,000), which enjoy less year-round sunlight and UV radiation than southern states such as Texas, Florida, Arizona, and New Mexico (

The rationale behind recommending using sunblock is that ultraviolet (UV) radiation is a known carcinogen and sunblock is designed to filter UV radiation. "Both UVA and UVB radiation is emitted by the sun, but because UVB was thought to be the primary causative agent of all skin cancers by direct damage to DNA, initial sunscreens were developed that blocked UVB with little or no protective effects against UVA. The sun protection factor (SPF) label on sunscreen relates to protection against UVB radiation and is not at all related to UVA radiation protection" based upon the assumption that UVB is deemed to be the primary culprit behind the development of skin cancer (Planta 2011). However, recent evidence indicates that UVA still is a factor in the development of melanoma due to its role in "oxidative stress, free radical generation, and the degradation of vitamin D" (Planta 2011). This is supported by the high rate of skin cancer amongst users of tanning beds even though this artificial light gives off a higher ratio of UVA to UVB than the sun itself. Some sunscreens do offer some UVB protection: benzophenones, titanium dioxide, or zinc oxide may provide greater UVA protection than conventional sunscreens. But even the most effective UVA blocker, titanium dioxide, blocks only 25% of UVA radiation (Planta 2011).

Given this evidence, it is easy to despair that there is no convincing evidence that any practice is prophylactic regarding sun exposure. However, some studies are promising: there is evidence that "chronic, low-grade exposure to sunlight may be protective against CMM" (Planta 2011). Studies of Austrian and German residents have found that individuals who did not have sunburn as children had a lower rate of CMM vs. those without frequent sun exposure. This would explain the higher rate of CMM in America amongst indoor workers in regions with low rates of sun exposure. Researchers have hypothesized that the sun can develop a protective tolerance to the sun, allowing the skin to tolerate UV radiation.

Such findings indicate that a deviation from current, standard recommendations regarding sunscreen use and sun exposure. At present, patients are usually advised to stay away from the sun, protect themselves on days with a high risk of sun exposure with sunblock and protective clothing, and avoid the sun if they are very fair-skinned. Although sunburn is still associated with a higher risk of CCM, prolonged outdoor activities in direct sunlight, so long as sunburns are avoided, may actually be protective against CCM.

However, the question arises as to why sunblock users have higher rates of CCM. One possible explanation is that individuals who use sunscreen may have a false sense of security and expose themselves to sunlight in a manner which increases their risk of burns. "In two European studies, sunbathers who used SPF 30 sunscreen sunbathed 19% to 25% longer than those using SPF 10. In a Danish study, 66% of sunburned people had used sunscreen to prolong time spent in the sun" (Planta 2011). Another explanation for the correlation is that individuals with skin types which are more prone to burning and who have had burns in the past are more likely to use sunblock. Regardless of the reason, the weight of evidence-based research indicates that emphasizing the use of sunblock alone, regardless of the SPF, will not have the desired result in reducing CCM for individuals with the highest risk factors.

Planta (2011) does note that some evidence-based research contradicts these findings. An Australian study found that "in consistent daily application of both UVA and UVB-filtering broad-spectrum sunscreen resulted in a decreased incidence of melanoma compared with control" (Planta 2011). It is possible that the improper use of sunblock (not using UVA-filtering block at all, allowing skin to burn through prolonged exposure) may be what is harmful and if individuals are highly motivated to use sunblock correctly, its full, promised effect can be enjoyed. Regardless, there are acknowledged contradictions in the extant studies which the author acknowledges.