Melanoma Thickness and Survival Trends in the United States, 1989 to 2009

Abstract

Background: With melanoma incidence rising and mortality stable, some question whether the melanoma epidemic is real. Melanoma thickness and survival trends may provide insights, but previous studies have been limited because of missing data on thickness.

Methods: With a validated imputation method for missing thickness data, we characterized melanoma thickness and survival trends among men and women in the Surveillance, Epidemiology, and End Results (SEER)-9 registries between 1989 and 2009. A total of 98,498 cases of invasive melanoma were identified. All statistical tests were two-sided.

Results: Incidence per 100 000 person-years increased (13.94, 95% confidence interval [CI] = 13.65 to 14.23, to 21.87, 95% CI = 21.56 to 22.19, P < .001) between 1989 to 1991 and 2007 to 2009, fatal incidence remained stable (2.32, 95% CI = 2.2 to 2.4, to 2.08, 95% CI = 2.0 to 2.2, P = .20) between 1989 to 1991 and 1998 to 2000, and five-year survival increased (88.29%, 95% CI = 87.60% to 88.95%, to 91.68%, 95% CI = 91.22% to 92.12%, P < .001) between 1989 to 1991 and 2001 to 2003. Increase in incidence occurred across all thickness groups. Median thickness decreased (0.73 to 0.58mm). Geometric mean thickness decreased (0.77 to 0.65mm) 4.6% (95% CI = 4.2% to 5.0%) every three years in multivariable analysis. Thickness decreased among T1/T2 tumors (0.01-1.00 and 1.01-2.00mm) and among all age and sex groups, whites, non-Hispanics, and all body sites. However, thickness increased among T3/T4 tumors (2.01-4.00 and > 4.00mm) and nodular melanomas; acral lentiginous melanomas approached statistical significance. Thickness remained unchanged among some racial minorities. Melanoma-specific survival improved (hazard ratio [HR] = 0.89, 95% CI = 0.88 to 0.91) every three years in multivariable analysis. Improvements in survival occurred across all subgroups except nonblack minorities, and nodular and acral lentiginous subtypes.

Conclusions: Increasing incidence across all thickness groups coupled with T3/T4 lesions becoming thicker suggests that the melanoma epidemic is real and not simply an artifact of increased detection pressure of earlier-stage T1/T2 lesions. Survival is generally improving independent of thickness, but improvements in survival have not been experienced by certain minorities, and nodular and acral lentiginous subtypes.