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August 6, 2005

BehindTheMedspeak: Melanoma is not becoming more common

Melanoma

What?

How can this be?

Everyone knows that the incidence of malignant melanoma (above) has skyrocketed in recent decades, a result of the increase in UV light reaching the Earth's surface due to loss of the ozone layer.

Right?

I mean, those are facts, not hypotheses, right?

Maybe not.

A study by scientists at Dartmouth University Medical School, published in the current (August 4) issue of the British Medical Journal, suggests that the incidence of malignant melanoma, the most feared of all skin cancers because of its propensity to spread before being diagnosed, has remained esssentially stable over the past 30 years.

Let's look at the numbers upon which the scientists based their conclusions.

1) In 2002 the incidence of malignant melanoma was six times that in 1950. (Keep reading.)

2) Between 1986 and 2001, the average rate of skin biopsy among people 65 and over in 9 geographical areas of the U.S. increased 2.5–fold.

3) Over this time, the average incidence of melanoma increased 2.4–fold.

4) The new cases found were virtually all early stage cancers.

5) The overall melanoma death rate remained stable.

The researchers concluded that the increased incidence of melanoma was largely the result of increased diagnosic scrutiny, not the result of an increase in the incidence of melanoma.

In other words, if you look with a higher powered lens, you're going to find more detail — but not more objects that you could otherwise see with the naked eye.

The standard mnemonic for melanoma surveillance is ABCD:

A = Asymmetry:
A_28


B = Borders (irregular):
B_40


C = Color (various):
C_37


D = Diameter (larger than a pencil):
D_20

**************************

The melanoma study cited above reminds me of the raging debate about prostate cancer and PSA: many of the nation's urologists believe a high PSA is bad and mandates surgical removal of the prostate; another large group of specialists believe prostate cancer to be a normal accompaniment of aging and that many more men die with than of prostate cancer: they advocate doing nothing in the asymptomatic patient.

August 6, 2005 at 12:41 PM | Permalink


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