Overall, the number of melanoma
cases is relatively small. Only 11 percent of the 1 million new
cases of skin cancer expected to be diagnosed in the U.S. this
year will be melanoma. But melanoma killed an estimated 8,110
Americans last year. And exposure to too much sun is often to
blame.
"We have really good studies on the effect of sun on skin cancer
and melanoma," said Dr. Michael Swann, a surgical dermatologist
and skin cancer specialist at Scripps Clinic in San Diego.
"There's no doubt, it's a huge risk factor, along with family
history."
There are many theories about how
sunlight works to destroy skin cells. Although genetics and the
amount of pigmentation in one's skin play roles, there's
disagreement about how much. It's true that lighter-skinned people
have more cellular skin damage and, thus, cancer risk than do
people with darker skin color.
Sunscreen can be protective
against most forms of skin cancer if used properly.
But some researchers, including
Cedric Garland, of the University of California San Diego Medical
Center's cancer prevention program, believe the increasing use of
sunscreens in the last 30 years has actually led to more skin
cancer.
That's because sunscreens prevent
people from getting sunburned, so they stay outside longer and are
exposed to more damaging ultraviolet rays.
"Sunscreens have allowed very
fair-skinned people to take vacations to Hawaii or the Bahamas and
spend two weeks soaking up the sun," Garland said. "That way they
rack up far more damage from ultraviolet A rays, to which
sunscreen is transparent."
Additionally, he said, sunbathers
don't use sunscreen properly. It washes off when they go swimming,
with sweat and with time - after a few hours of lying in the sun.
The U.S. Food and Drug
Administration has proposed more stringent labeling requirements
for sunscreen makers.
There are two kinds of ultraviolet
light. Currently, manufacturers are only obligated to label
products for their ability to block UVB rays, ultraviolet light
that causes sunburn. Now, products are labeled with SPF numbers
between 2 and 30-plus.
The new regulations would require
manufacturers to give scientific proof of any claim about the
strength of UVB blocking power up to SPF 50-plus.
Additionally, the FDA would set
new standards for proof for the second kind of ultraviolet light,
UVA rays, which are considered more damaging because they cause
cellular changes to layers of skin much deeper than UVB. UVA is
suspected of being the underlying cause of many cases of melanoma.
As proposed, the FDA's new rules
are expected to rank the power of a sunscreen product's UVA
protection from one to four stars.
They would caution sunscreen
customers about the importance of covering their skin and wearing
hats with wide brims for better protection against the sun, and to
reapply sunscreen after swimming or perspiring, said Rita
Chappelle, FDA spokeswoman.
The rules also would increase
product testing requirements, giving manufacturers one year to
document that their products indeed give the protection claimed.
Both test tube and human studies will have to be done.
"There's a lot of misinformation
about sunscreen out there," Chappelle said. "We want to make sure
the public has the correct information."
Ironically, many researchers
believe that sunscreens are really useful only against the more
common, less-lethal types of skin cancer - basal or squamous cell
cancers - but not against melanoma.
"At one level, sunscreens are
troubling, because they send the message that they're sun
protective," said Dr. Gregory Daniels, melanoma program
coordinator at the Moores Cancer Center at UC San Diego.
"Sunscreen has not demonstrated any benefit for preventing
melanoma skin cancers, and they're the most deadly."
While the greater the sun
exposure, the greater one's risk for getting melanoma, that's not
true for people who work every day in the sun, such as farmers,
Daniels said. They seem to be protected, perhaps because their
systems develop an immunity or they aren't subjected to bursts of
ultraviolet light.
"It's the people who get
intermittent blasts of sun, people who get it from weekend
exposure or while on a vacation that have a higher risk," Daniels
said.
One thing is clear from all the
studies, however. Early detection of all skin cancers, and
specifically melanoma, has an extremely successful rate of cure.
And that field of research is
progressing fast.
At Scripps Clinic and elsewhere,
doctors are trying to find better ways to look more deeply into
the skin to find precancerous cells and, by doing so, avoid
unsightly biopsies.
A big emphasis is on finding a
safe way to kill precancerous cells before they become cancerous,
Swann said. A two-step outpatient technique called "photodynamic
therapy" is one effort he nicknamed "the smart bomb" approach
against squamous cell carcinoma.
The patient is injected with a
light-sensitive drug. A day or two later when the drug has been
absorbed into the bloodstream and skin cells, a laser light is
directed onto the patient whose precancerous cells are exposed in
a certain spectrum.
The light signals the drug to
destroy the cells without damaging surrounding tissue.
The big fear in skin cancer is
still melanoma, which is so important to catch early. "We can take
someone with this disease that has spread to multiple organs and
cure them, but it's a low rate of cure," Daniels said.
