The melanoma risk factors of high naevus count, red hair alleles and the freckling pale skin associated with the MC1R genotype act synergistically to confer an extremely high lifetime risk of melanoma that warrants intensive screening, Queensland dermatologists say.
While these risk factors are well known to individually increase risk of melanoma, the Brisbane Naevus Morphology Study has shown that in combination they confer a 25-fold or higher increased melanoma risk compared to people with fewer risk factors.
For Queensland residents this translates into an absolute risk of melanoma of 23.3% for males and 19.3% for females, according to findings published by Associate Professor David Duffy and Professor Peter Soyer from the Dermatology Research Centre, The University of Queensland Diamantina Institute.
In their analysis of data from 1267 patients treated for melanoma at dermatology clinics in Brisbane they found that compared to individuals with dark brown hair and 0-4 naevi, individuals with red hair and 20+ naevi had a 10-fold high risk of melanoma (Odds Ratio 10.0).
Individuals with the MC1R R/R genotype and 20+ naevi ≥5mm had a 25-fold higher risk of melanoma (OR 25.1) compared to MCR1 WT/WT individuals with 0-4 naevi.
The highest risk group was men with MC1R R/R genotype and 20+ moles, who had an absolute risk of melanoma to age 75 of 23.3%, compared to 0.8% for men with MCR1 WT/WT genotype and 0-4 naevi.
“Patients with many large naevi and the red hair colour phenotype, particularly those with an MC1 RR/R genotype, have an unusually high risk of melanoma,” they wrote.
The synergistic effects of the risk factors create a population who would be suitable for regular melanoma screening, they suggest.
“While regular screening of the general population is not recommended, several national bodies do recommend physician-led screening for people in high risk groups, as this approach can improve the benign-to-malignant ratio of excisions, improve early detection rates, and reduce overall costs by preventing the need for high-cost treatment of metastatic melanoma,” they noted.
“In a high UV environment this risk [for those with combined risk factors] exceeds the threshold recommended for screening in other cancers, and such individuals should undergo intensive, regular physician-led surveillance,” they conclude.
The results are published in the British Journal of Dermatology.