Recent cohort trends in malignant melanoma by anatomic site in the United States

The incidence of malignant melanoma has been increasing steadily in the United States. The increase may be due to lifestyle changes in subsequent generations or birth cohorts. The nine population-based tumor registries in the Surveillance, Epidemiology, and End Results program (SEER) have been in existence for a sufficient time to begin to investigate cohort trends for the US population. Cases were the 18.787 Caucasians aged 20 to 84 years, who reported to SEER registries with a diagnosis of melanoma in 1974-86. Among men born between 1890 and 1919, each subsequent five-year birth cohort experienced 45 to 57 percent increases in age-adjusted melanoma incidence of the arm and trunk, and 14 to 20 percent increases were experienced across each site (arm, leg, head, and trunk) for the 1920-44 cohorts of men. Among women born between 1890 and 1919, 24 to 29 percent increases were seen for melanoma of the trunk, arms, and legs for each subsequent five-year birth-cohort, followed by six to 29 percent increases in the 1920-44 cohorts. Recent birth cohorts, 1945-64, have shown stabilizing rates, even after an attempt to adjust for the increasing tendency for diagnoses to be made in doctors' offices. Thus, the dramatic birth-cohort effects appear to have ended beginning with those born in 1945. However, melanoma rates will continue to rise until those born after 1945 represent the majority of the population. Furthermore, for the most recent cohorts, the trunk has become the most common site (per square meter of body surface) for men and the second most common site for women. This suggests that some lifestyle change has led to more damaging exposure (e.g., sunburns) of the trunk among recent cohorts than earlier cohorts.