Sunscreen can help reduce the risk of malignant melanoma, contrary to
the finding of a study that received considerable media attention
last February, says a skin cancer specialist at Ohio State
Universitys Arthur G. James Cancer Hospital and Research Institute.
"If youve heard or read comments to the effect that
sunscreens do not protect against malignant melanoma, forget
them," said Ronald Siegle, a specialist in skin cancers of the
head and neck.
"There is very strong epidemiological evidence linking sun
exposure to malignant melanoma, and there is evidence that sunscreens
do provide protection."
"We know for sure that sun exposure causes the two most common
forms of skin cancer--basal cell and squamous cell carcinoma--and
that sunscreen protects people from these malignancies," he added.
Comparing Apples and Oranges
The February study, which was presented at a scientific conference
but never published in a peer-reviewed journal, suggested that
sunscreen fails to protect against melanoma and may even increase
ones risk of developing it.
"But that study was severely flawed by too many suppositions and
extrapolations," said Siegle.
For example, it looked at the findings of five earlier studies, four
of which were concluded prior to 1980, before sunscreens with a sun
protective factor (SPF) of 15--the minimum recommended
"Its like comparing apples and oranges," said Siegle.
Caucasians with pale complexions are at greatest risk of sun-related
skin cancers (the risk of melanoma is 70 times greater for whites
than it is for dark-skinned blacks, although they, too, can develop
this malignancy on the palms of the hands, soles of the feet, and
under the nails).
Continue to Be Sun-Smart
"People should continue to be sun-smart," said Siegle.
"Limit your amount of sun exposure, use a sunscreen of SPF 15 or
greater on exposed skin, protect exposed skin with clothing if
youre going to have excessive sun exposure, and wear a hat and sunglasses."
Epidemiologic studies provide the primary evidence linking sun
exposure to malignant melanoma.
"The latitude in which one lives is one major factor," he
said. "The closer to the equator, the more melanoma there is.
The incidence of melanoma among fair-skinned people is higher in
Miami than among the same group in Sioux Falls, South Dakota, for example."
Other evidence of the association between sun exposure and melanoma
comes from looking at the skin type of people who develop the
malignancy: People who have the highest incidence of melanoma tend to
have the most sun-sensitive skin. These people typically have
light-colored hair and eyes, and light skin that tends to freckle
rather than tan.
The exact mechanism by which sun exposure triggers melanoma is not
known yet, but intermittent, strong exposures that result in severe
sunburns are strongly associated with it.
"Again, when you look at who gets melanoma, its not so
much the farmer or construction worker whos outdoors all day;
its the person who works indoors all week, then, when the
weekend comes, sheds his shirt to work in the garden, or dons a swim
suit and goes to the beach, and gets a sunburn. Melanoma is strongly
associated with these so-called recreational exposures."
Data from Australia Confirms Protective Effect of Sunscreens
Evidence that sunscreen protects against melanoma comes from
Australia, which has one of the highest rates of malignant melanoma
in the world: more than 50 cases per 100,000 people vs about 12 per
100,000 people in the United States. Recently, however, the rate of
melanoma in Australia has begun to plateau. Public health officials
believe that the rate is slowing because of a greater use of
sunscreens and protective clothing to reduce sun exposure.
"We have strong reason to believe that sunscreens protect
against basal and squamous cell carcinoma, and they clearly minimize
the formation of precancers and aging changes in the skin," said
Siegle. "If ultraviolet light causes malignant melanoma,
its also reasonable to believe that sunscreens protect against
malignant melanoma, too."
Because 20 years can elapse between a disease-causing exposure and
the appearance of melanoma, definitive studies take time, said
Siegle. "The sun exposure people got in 1985 is likely to be
responsible for skin cancers that arise in 2005 and later."
Malignant melanoma is the least common of the three main types of
skin cancer, with 41,600 new cases expected in 1998 (as compared to
600,000 new cases of basal cell carcinoma and 200,000 new cases of
squamous cell carcinoma).
"Early diagnosis is important," said Siegle. "Over 80%
of melanomas are cured, and when theyre found early,
essentially all of them are cured."