Background
The incidence of melanoma has been increasing faster than that of any other cancer in the United States. It is unclear whether the increase is related to increased surveillance or other changes in the disease.

Objective
To examine changes in melanoma rates by several measures of severity of disease and to review the ways in which increased surveillance may cause lead-time bias through early detection or length bias through detection of clinically insignificant lesions as a basis for interpreting these changing rates.

Design
Population-based incidence rates for 1973 through 1994.

Setting
United States Surveillance, Epidemiology, and End Results Program tumor registries.

Patients
A total of 47,638 cases of melanoma among white patients aged 20 years and older.

Main Outcome Measures
Relative incidence rates for melanoma by stage, and tumor thickness adjusted for age and sex.

Results
Localized-stage melanoma increased, but no significant change for distant-stage melanomas was seen. Among those diagnosed from 1988 through 1994, there were 22%, 26%, and 31% increases for tumor thickness less than 1.0 mm, between 1.0 and 3.0 mm, and 3.0 mm or greater, respectively. The 2-year mortality rates also increased over time.

Conclusions
While these data show large increases in early disease (localized stage, thin tumors), they also suggest some increase in advanced disease (thick tumors, 2-year mortality). This indicates that the increasing incidence rates of melanoma are not solely caused by increased early detection and diagnosis of clinically insignificant melanomas, but may also represent a true increase in cancer rates.

Comment:

The incidence of malignant melanoma is increasing faster than any other cancer in the United States.  If current trends continue, it is estimated that 1 of every 75 people born in the year 2000 will develop melanoma.  This is an astounding increase.    In 1973, the incidence of melanoma was 5.7 cases per 100,000.  By 1994, it had increased to 12.5 cases per 100,000.  During the same period, the mortality per 100,000 increased from 1.6 to 2.2. This article examines the population based incidence rates through a survey of 47,638 cases of melanoma diagnosed among adult white patients. The study did find an increase in early stage thin melanomas, presumably a direct result of increased awareness on the parts of the diagnosing physician and patient. Somewhat surprising was the increased incidence of advanced disease melanomas, suggesting a true increase. Some experts have noted a different biological behavior in thin melanomas versus thick melanomas. Indeed, if this is true, we may also be witnessing an increase in aggressive melanomas which may not be diagnosed at the early totally curable stage. Further investigation into the molecular biology of this neoplasm may shed additional light to deciphering which melanomas and patients are at increased risk for advanced disease.

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