Background Study on risk of subsequent melanoma among melanoma patients is scarce.

Objective To investigate melanoma risk in melanoma patients.

Material and Methods Netherlands Cancer Registry incidence data (1989–2008) were employed. Patients (N=57 817) diagnosed melanoma in this period were followed. Follow-up censored at second melanoma, death or end of study. Standardised incidence ratio (SIR) was used expressing RR compared to the general population. Sex-and follow-up-specific SIR were computed under for both first and second in situ and invasive melanomas. Cox regression model which contains age at diagnosis, sex, Breslow thickness, and follow-up periods was constructed to estimate relative excessive risk melanoma risk.

Results During a median of 3 yrs of follow-up time, 1985 patients diagnosed for a second melanoma. After both in situ and invasive melanoma, inflated risk for a second melanoma was observed: after a first in situ melanoma, the risk to develop a subsequent melanoma was 16.3 (SIR), 95% CI 14.7 to 17.9. Following an invasive melanoma, risk was 13.3 (SIR), 95% CI 12.6 to 14.1. Elevated risks were observed in all follow-up periods (0–1 yr, 2–5 yr, 6–10 yrs, 10–15 yrs, 16–20 yrs) in both sexes. Age at diagnosis, sex, Breslow thickness, were shown to explain the excess risk observed in those follow-up periods.

Discussion and Conclusion Based on the persistently high risk of melanoma among melanoma patients, a long-term follow-up schedule is needed for both patients and clinicians.