SAN DIEGO (FRONTLINE MEDICAL NEWS) U.S. incidence rates of malignant melanoma in adolescents fell by nearly half during 2000-2014, based on information from a National Cancer Institute database.

The substantial drop in new cases of malignant melanoma in Americans aged 10-19 years over the most recent 15-year period with data available contrasts with a stable rate among children aged 0-9 years, and a steadily rising rate among adults during the same period, Ryan C. Kelm said at the annual meeting of the American Academy of Dermatology.

The findings also confirmed that malignant melanoma is significantly more common in girls, regardless of whether they are aged 0-9 years, or 10-19 years. In addition, girls aged 10-19 years have significantly better 5-year relative survival, compared with boys that age, with rates of 97% and 93%, respectively, said Mr. Kelm, a researcher in the department of dermatology at Northwestern University, Chicago. Relative survival after 5 years among girls and boys aged 0-9 years was 94%. These rates were up from those reported for 2001 in the SEER (Surveillance, Epidemiology, and End Results) Program, when 5-year relative survival was 89% among all children and 92% among all adolescents ( J Clin Oncol. 2005 July 20;23[21]:4735-41 ).

Mr. Kelm and his associates studied U.S. data compiled from 2000 to 2014 by the SEER Program, maintained by the National Cancer Institute. They identified 1,796 patients aged 0-19 years diagnosed with malignant melanoma (218 children and 1,578 adolescents). The overall incidence rate for the entire 15-year period was just over 1 case per million among children and just under 9 cases per million among adolescents. In contrast, the adult U.S. incidence rate estimates for 2018 are pegged at 260 per million among non-Hispanic whites, 40 per million among Hispanics, and 10 per million among black Americans, according to the American Cancer Society.

An additional analysis showed a notable difference in incidence rates over the 15-year period studied, depending on age. In children aged 0-9 years, the annual incidence rate held roughly steady at just under 2 cases per million throughout the 15 years. But among adolescents, the rate fell over time, from about 10-12 cases per million during 2000-2004 to about 5-7 cases per million during 2010-2014. In 2001, the rate was about 11 cases per million, and in 2013, the rate was about 6 cases per million. This contrasts with the adult rate, which has “risen rapidly over the past 30 years,” according to the American Cancer Society’s 2018 report.

The SEER data also showed that distribution of melanoma histologic types differed by age. Among adolescents the most common identified form was “superficial spreading,” in 32%, with nodular in 6%, mixed epithelioid and spindle cell in 2%, and “not otherwise specified” in 54%. In children, the most commonly identified form was mixed epithelioid and spindle cell, in 10%, followed by nodular in 9%, and superficial spreading in 9%, with 63% not otherwise specified.

SOURCE: Kelm RC et al. AAD 18, Abstract 6722.