Risk of second primary in situ and invasive melanoma in a Dutch population-based cohort: 1989-2008

Background Patients with melanoma are at increased risk of developing a subsequent melanoma. Objectives To estimate the risks of developing a second primary in situ or invasive cutaneous melanoma after a first melanoma, between 1989 and 2008. Methods Patients were followed until diagnosis of a second melanoma, date of death or end of study. Cumulative risks, standardized incidence ratio (SIR, observed second melanomas divided by background age-, calendar- and sex-specific incidence rates of melanoma, as recorded in the Netherlands Cancer Registry) and absolute excess risk (AER, observed minus expected per 10 000 person-years) of second melanomas were calculated. Results In total, 10 765 patients with in situ melanoma and 46 700 with invasive melanoma were included. The cumulative risks of a second invasive melanoma after a first in situ or invasive melanoma at 20 years of follow-up were 6.2% and 5.0%, respectively. The relative risk of developing any melanoma (in situ or invasive) after any first melanoma (measured as SIR) varied from 12.4-fold [invasive after invasive melanoma; 95% confidence interval (CI) = 11.613.2] to 26.4-fold (in situ after in situ melanoma; 95% CI = 22.630.7) increase compared with the general population. SIRs and AERs remained elevated up to 20 years after the first melanoma. Conclusions This study shows significantly increased long-term risks (both relative and absolute) of developing a second invasive melanoma after a first melanoma (invasive and in situ), and might serve as a basis for follow-up guidelines.