TRENDS IN THE POPULATION-BASED INCIDENCE OF SQUAMOUS-CELL CARCINOMA OF THE SKIN FIRST DIAGNOSED BETWEEN 1984 AND 1992

Objective: To examine the incidence of first diagnosis of invasive squ amous cell carcinoma (SCC) of the skin over time. Design: Retrospectiv e, population-based incidence study. Setting: Enumerated, geographical ly isolated, semiurban population served by the Mayo Clinic and its af filiated hospitals and the Olmsted Medical Center, including its affil iated hospital in Rochester, Mim. Methods: Using the Rochester Epidemi ology Project databases that capture virtually all medical care provid ed to the residents of Rochester, we identified and reviewed records o f all documented residents in whom histologically proven, invasive SCC of the skin was first diagnosed between 1984 and 1992. Age and sex st ratum-specific rates were calculated, and age-adjusted rates observed over time for individuals aged 35 years or older were analyzed using P oisson regression. Adjusted rates were compared with the results of ot her studies. Results: Review of 1630 records identified 511 incidence cases of SCC. Tumors located on the:head nd neck accounted for 66.4% o f tumors in females and 72.9% in males. The annual age- and sex-specif ic incidence rates per 100 000 increased from 0 cases among males aged 0 to 14 years to 1286.0 cases among males aged 85 years or older. Ove r time, the annual age-adjusted incidence rates per 100 000 females ro se from 46.5 (95% confidence interval [CI], 32.4-60.6) for the 1984 to 1986 period to 99.6 (95% CI, 80.4-118.7) for the 1990 to 1992 period and were 71.2 (95% CI, 61.7-80.8) overall. The corresponding rates for males were 125.9 (95% CI, 95.3-156.4), 191.0 (95% CI, 156.9-225.0), a nd 155.5 (95% CI, 137.0-174.0). The age- and sex-adjusted SCC incidenc e rates for the period from 1987 to 1989 and 1990 to 1992 exceeded tho se for the period from 1984 to 1986 (P=.03 and P<.001, respectively). Our age-adjusted rates for SCC were within the ranges seen in other wh ite populations from temperate climates. Conclusion: The frequencies o f first diagnosis of SCC are increasing at rates beyond those explaina ble by demographic shifts alone.