Clinical and sociodemographic characteristics associated with thick melanomas. A population-based, case-case study in France.

Objective: To identify clinical and sociodemographic factors associated with very thick melanoma (VTM) (Breslow thickness, 3 mm) in France.

Design: Retrospective, population-based, case-case study using a survey of cancer registries and questionnaires to practitioners.

Setting: Five regions covering 19.2% of the French territory and 8.2 million inhabitants.

Cases: Cases included all incident melanomas with a Breslow thickness of 3 mm or greater (ie, VTM), diagnosed between January 1 and December 31, 2008, in residents of the study area (Alsace, Bourgogne, Champagne-Ardenne, Franche-Comte', and Lorraine, France), and a randomly selected sample of melanomas thinner than 3 mm.

Main outcome measures: Circumstances of diagnosis,clinical and pathological characteristics of melanomas,and sociodemographic characteristics of patients(age, sex, residence, home and family life conditions, educational level, and smoking habits).

Results: Among 898 melanomas, 149 (16.6%) were VTMs. Very thick melanomas were more often diagnosed in a general-practice setting than thinner melanomas.The rate of immediate clinical recognition by dermatologists was lower for VTMs than for thinner melanomas. In a multivariate logistic regression analysis,factors associated with VTM were the nodular and acrolentiginous types; the head and neck and lower limb locations; older age; male sex; and being single, separated,divorced, or widowed. When only factors related to patients were taken into account, older age, male sex,and living alone were independent risk factors for VTM.The most significant risk was observed for patients living alone.

Conclusions: Intrinsic factors related to the tumor and socio demographic characteristics of patients contribute to the occurrence of VTM. These factors should be better targeted in future secondary prevention programs.