Module 11:Epidemiology of Melanoma
Objective:
Learn more about the current trends in melanoma.
Melanoma is the most
serious skin cancer. It can even kill. But melanoma can be prevented. And
it can be treated if found early.
Melanoma
Rates Are Going Up
In 2001—
- There were 51,400
new cases of melanoma found in the United States.
- Melanoma caused
about 7,800 deaths in the United States.
The incidence of
melanoma has gone up by 4 percent a year since 1973. We don't know all the
reasons for this rapid increase. But scientists suspect that the following
play an important role:
- more total exposure
to the sun
- changing patterns of
exposure
Incidence by Race and
Location
The incidence of
melanoma among whites goes up as you get nearer the equator. The world's
highest melanoma rate is in Australia. Melanoma is not common in
darker-skinned people, such as those of African or Asian background. But
darker-skinned people can still get melanoma. They often develop the
disease at sites not exposed to the sun. These include the nail beds and
soles of the feet.
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Risk Factors for Melanoma
There are several known risk factors for melanoma. They include—
- sun exposure
- skin type (I, II, III, etc.)
- skin, hair, and eye color
- freckling
- number and type of moles
- personal and family history
Sun Exposure
There is very strong evidence that sun exposure can cause skin cancer.
Ultraviolet (UV) rays damage DNA and cause tumors. But different patterns
of sun exposure tend to cause different cancers.
Long-Term Sun Exposure Vs. Short "Bursts"
Squamous cell carcinomas are linked to total sun exposure over time. But
melanomas and, more recently, basal cell carcinomas are linked to
"short, intense exposure."
Squamous cell carcinomas usually occur in skin areas that get the most
sun over long periods of time. Examples are the face and back of the hands
and forearms. Basal cell carcinomas usually occur on the face, but
recently, more and more are showing up on areas that are not chronically
exposed to the sun. On the other hand, melanoma usually appears in areas
exposed to the sun intensely for short periods. Examples are the trunk in
males and the lower legs in females. Melanoma is also more common in
people who get sun only in intense bursts on weekends and vacations.
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How the Incidence of Skin Cancer Depends on the Pattern
(short bursts or over a long period of time) and the Amount of Exposure
[ Text Description ]
Reprinted from the Journal of Photochemistry &
Photobiology B, Vol 63, 2001, pp 8-18, Armstrong: "The
epidemiology of solar radiation and skin cancer", figure 5, with
permission from Elsevier Science.
Skin Type, Coloring, Freckling, and Moles
Physical traits linked with a higher risk for melanoma include—
- fair skin
- skin that burns easily
- light eyes (blue/green/gray)
- blond or red hair
- freckling
Having a lot of moles can also raise risk. This is especially true if
you have any oddly shaped moles. Moles are also called "nevi."
Oddly shaped nevi are referred to as "atypical." Most moles
develop from sun exposure in childhood. So having a lot of moles may mean
that you got a lot of sun as a young child. About 40 percent of melanomas
begin in existing moles. So checking moles for the "ABCDs" of
melanoma is an important step toward early detection. (The ABCDs of
melanoma were covered in module 10. They are
Asymmetry, irregular Border, uneven Color, and Diameter larger than a
pencil eraser.)
To see some examples of "benign," or non-cancerous, nevi and
melanoma, go to http://www.skincarephysicians.com/melanomanet/skin_lesions.htm.*
Personal and Family History
You have a higher risk of melanoma if you or someone in your family has
ever had the disease.
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Words to the Wise
Some very important risk factors for melanoma can be changed. You can
lower risk by preventing—
- unprotected sun exposure, especially intense, "off and on"
exposure
- sunburns early in life
Just a few bad sunburns in childhood or young adulthood can raise your
risk for melanoma. We are all born with physical traits that we can't
change. But we can change what we do. You can reduce your risk of melanoma
by protecting yourself from the sun's ultraviolet rays.
Go back to the Web site http://seer.cancer.gov
to see how the incidence of melanoma has gone up over the last 25 years.
Step 1: From the "Choose a Cancer Site" pop-up menu,
choose "Melanomas of the Skin."
Step 2: Under "Incidence," find "Line Charts
Displaying Age-Adjusted (1970 U.S. Standard Population) SEER Incidence
Rates for Individual Years: Nine Registries for 1973-1998."
Step 3: Click on rates for [All Ages] by Sex, then by Race, then by
Race and Sex. In what groups have the incidence rates gone up? Why do you
think so?
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