Family History Predicts Lifetime Melanoma Risk

Knowing an individual’s family history of melanoma may allow clinicians to calculate their lifetime cumulative risk of diagnosis

medwireNews: An individual’s lifetime cumulative risk of melanoma (CRM) is significantly influenced by the number of close relatives who have been diagnosed with any form of the skin cancer, reveals population data from five Nordic countries.

The overall CRM was between 2.5% and 3.0% for patients with a first-degree relative who was diagnosed with superficial spreading (SSM), nodular (NM), or lentigo maligna forms of melanoma between 1955 and 2010, giving an approximate twofold increase in risk compared with the general population.

The CRM increased further if multiple relatives were affected, from 3% for individuals with one relative diagnosed before the age of 30 years to 14% for those with two affected relatives. The CRM was 6% for those with two relatives diagnosed between the ages of 30 and 59 years and 5% for those with two relatives diagnosed at age 60 years or older.

And for individuals with a same-sex twin diagnosed with melanoma, the CRM was between 7% and 21% depending on age at diagnosis, report Mahdi Fallah, from the German Cancer Research Center in Heidelberg, and co-workers.

The team did not find any concordant familial cases of acral lentiginous melanoma, desmoplastic melanoma, compound nevus, spindle cell melanoma, or malignant blue nevus but this may be due to the rarity of these forms, the researchers say.

Familiar risk did not just occur for concordant types of melanoma, however. For example, an individual with a first-degree relative with NM also had a significantly higher risk of developing SSM or acral lentiginous melanoma, with standardised incidence ratios of 2.6 and 4.0, respectively.

“Our finding may suggest that the role of genetic or environmental factors in the differentiation of histological types of melanoma is not as strong as its role in the development of melanoma as such,” the researchers write in the European Journal of Cancer.

“In other words, histological type of melanoma does not seem to play an important role in familial melanoma and vice versa.”

Mahdi Fallah and team observe that it is difficult to distinguish between the genetic influence of susceptibility genes for melanoma, the impact of familial patterns of hair, skin and eye colour, and a shared history of environmental factors between family members, such as area of residence and holidays.

“However, the strength of this study is that estimated familial risks could be used in the clinic regardless of the exact underlying reason for them,” they conclude.

The study included registry data for 238,724 first-degree relatives of 46,091 melanoma patients from Denmark, Iceland, Norway, Sweden and Finland. CRM was calculated to be across 0 to 79 years according to Nordic life expectancy.

Reference

Fallah M, Pukkala E, Sundquist K, et al.  Familial melanoma by histology and age: Joint data from five Nordic countries. Eur J Cancer; Advance online publication January 23rd 2014.

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