Analysis of the Melanoma Epidemic, Both Apparent and Real

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.