Rising melanoma incidence rates of the trunk among younger women in the United States

Abstract

Background: Melanoma rates are rising among young women, possibly due to increasing UV radiation to previously protected body sites. Therefore, we examined melanoma incidence trends by age, gender, and body site. Descriptive methods were complemented with the age-period-cohort parameters net drift and longitudinal age trend.

Methods: Case and population data were obtained from the Surveillance, Epidemiology, and End Results (SEER) 9 Registries Database (1975-2006). Net drift summarized the average annual percentage change in log-linear rates per year of calendar-time (or year of diagnosis). Longitudinal age trend summarized the average annual percentage change by attained age at diagnosis. Early- and late-onset melanomas have low and high longitudinal age trends, respectively.

Results: There were 105,829 melanomas diagnosed in the SEER 9 Registries. The overall age-adjusted incidence rate (IR) for melanoma was 17.7/100,000 person-years. Age-specific IRs were greater among women than men prior to age 40 years. Among women, IRs decreased for all anatomic sites relative to the trunk. The highest net drift occurred in truncal lesions among women (net drift, 3.8%/year of calendar time; 95% confidence interval, 3.5-4.0%). The lowest longitudinal age trends also were observed for truncal lesions among women (longitudinal age trend, 5.4%/year of attained age; 95% confidence interval, 5.1-5.7).

Conclusions: Although melanoma IRs overall have risen for decades, the combination of high net drift and low longitudinal age trend show that melanomas are rising preferentially on the trunk among young women.

Impact: Future surveillance and analytic studies should consider melanoma effect modification by age, gender, and body site.

Figure 1

Age-period-cohort parameters for invasive cutaneous melanoma by gender and anatomic body site (SEER 9; 1975-2006). A: Net drift point estimates and 95% confidence intervals (in brackets). Net drift is a summary measure of the overall linear trend in the period + cohort effects. It is closely related to the estimated annual percentage change in the age-standardized incidence rate, see text for details. B: Longitudinal age trend point estimates and 95% confidence intervals (in brackets). Longitudinal age trend is a summary measure for the overall linear trend in the age + period effects. Low longitudinal age trends represent tumors that develop early in life; high longitudinal age trends reflect tumors that develop late in life.