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Guidelines for Genetic Testing for Melanoma
Is it necessary to update guidelines for genetic testing for melanoma in countries with low to moderate incidence?
Genetic testing for melanoma-prone mutation in France (a country with low to moderate incidence of melanoma) is proposed in cases with two invasive cutaneous melanomas in the same patient, or in first- or second-degree relatives. In preclinical studies, these rules led to disclosure of mutation(s) in more than 10 per cent of these families, the threshold widely accepted to justify genetic testing for cancers.
A study – published in JAMA Dermatology – reconsidered these criteria in a general population testing of patients. The retrospective study looked at 1,032 patients who underwent genetic testing for melanoma between 2004 and 2015.
The mutation rate was 67 of 1,032 patients (6.5 per cent). Their average age was 54.5 years, with a range of 18 to 89 years.
This rate increased to 38 of 408 patients (9.3 per cent) when applying a rule of 3 – that is, those with three or more primary melanomas. The rate further increased to 27 of 150 patients (18 per cent) with a rule of 4.
The impact of age at first melanoma was observed only in those younger than 40 years, with a rate of 32 of 263 (12 per cent) for the rule of 2, and 22 of 121 (18.2 percent) for the rule of 3.
Using the rule of 2 in patients younger than 40 years reduced the number of missed CDKN2A-mutated families when applying the rule of 3 from 32.5 percent to 16.2 per cent. Anamnestic uncertainty, found in 88 families (8.5 per cent), if excluded, would have led researchers to withdraw only 21 cases (23.8 per cent), and only one mutation would have been missed.
Researchers proposed using the rule of 3 to recommend genetic testing in France and countries with low to moderate incidence of melanoma, except in families and patients with a first melanoma occurrence before age 40 years in whom the rule of 2 could be maintained.
Delaunay J, Martin L, Bressac-de Paillerets B, Duru G, Ingster O, Thomas L. Improvement of Genetic Testing for Cutaneous Melanoma in Countries With Low to Moderate IncidenceThe Rule of 2 vs the Rule of 3. JAMA Dermatol. 2017;153(11):1122–1129. doi:10.1001/jamadermatol.2017.2926
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