Study: Worldwide Incidence of Malignant Melanoma Continues to Increase

An important new study recently published online in JAMA Dermatology points to an alarming increase in the incidence of malignant melanoma (MM). In Denmark, the study shows, the incidence of MM has doubled during the past 25 years, despite targeted awareness campaigns and a focus within the dermatology community on early detection and treatment.

The study authors used the official national Danish Melanoma Group database to describe all eligible, prospectively registered cases of in situ and invasive melanoma in Denmark from January 1, 1985, through December 31, 2012.The review included 3,299 cases of in situ melanoma and 20,760 cases of MM. The incidence (95% CI) of MM increased by 4.5% (3.6%-5.3%) for men and 4.3% (3.5%-5.2%) for women, and the growth in incidence was especially pronounced in patients older than 60 years.The increase in MM incidence for those over age 60is commonly accepted to be due to those who received early UV exposure at a time when there were fewer primary education campaigns regarding skin cancer.

While these findings are not necessarily surprising, they are certainly alarming. Not only is the worldwide incidence of MM increasing, so is mortality.The authors note, “In most countries, mortality rates are rising, except in the United States and Spain, where mortality has remained stable and even decreased for patients younger than 65 years. From 1985 through 2011, MM-related mortality in Denmark increased for men, whereas MM-related mortality for women remained stable, and 5-year survival rates increased.”

This is one of the first—and certainly one of the most extensive—national studies to examine changes in the incidence of MM over time. Perhaps more importantly, the study authors take aim at a common misperception in the incidence of MM: that increased numbers reflect a greater awareness of MM, leading to increased diagnosis, overdiagnosis, and diagnostic drift (wherein different physicians have differing diagnoses for the same patients). According to the study authors, “If these consequences of greater awareness were true in Denmark, we would see an increase in thin and in situ melanomas and a decrease in thick melanomas and mortality, as shown after a large screening program. Most studiesreport an increase in melanomas of all [Breslow thickness] (BT),* but with a relatively greater increase in in situ melanoma and thin MM compared with thick MM… This observation and the persisting increase in male mortality and incidence of thick and intermediate MM (BT, >1.00 mm) suggests that the increase in incidence is not caused solely by increased diagnoses but is, at least in part, a true phenomenon.”

“A relative increase in in situ melanoma, thin MM, and 5-year survival rates with a decrease in ulcerated tumors indicates that secondary interventions, such as early detection and treatment, are most likely effective,” the authors write. Nevertheless, the unabated increase in MM incidence suggests much opportunity for intensifying primary prevention through early education efforts aimed at young adults, adolescents, children, and parents of young children.

*Breslow thickness is a description of how deeply tumor cells have invaded.