The risk and risk factors of a second non-melanoma skin cancer: a study in a Mediterranean population.

BACKGROUND: Non-melanoma skin cancer (NMSC) patients often develop second primary skin tumours. Studies assessing the risk and risk factors on the appearance of a second NMSC are scarce, especially in European countries.
OBJECTIVES: To assess the 5-year risk of a second NMSC in a Mediterranean population, and to find patient characteristics predicting second tumours.
METHODS: NMSC patients at our institution were studied retrospectively. In situ tumours, recurrences, follow-up shorter than 2 months and mucosal lesions were excluded. Data analysed included age, gender, anatomical site, histological subtype, number of tumours and months of follow-up. Disease-free interval was defined as time from histological documentation of the first NMSC to the date of the last follow-up or to the date of histological documentation of the second NMSC. Survival analysis was conducted with the life-table analysis. Cox's proportional hazards regression model was used to assess risk factors.
RESULTS: The study group comprised 535 cases. Of these, 120 patients presented a second NMSC (22.4%). Hazard rates remained high in all yearly intervals. Multivariate analysis showed older age, multiple tumours and male sex as significant prognostic factors. When the second NMSC was diagnosed in the first year of follow-up, a trend to a high risk of further NMSCs was observed.
CONCLUSIONS: The risk of a second NMSC is similar to other studies, although in the lower range. Prognostic factors are also similar to other studies. Yearly hazard rates not falling suggests that long-term follow-up is needed. Prospective studies including whole-body examination could define the exact risk of a second NMSC.