Increased incidence of second primary melanoma in patients with a previous cutaneous melanoma

Patients with cutaneous melanoma reportedly have an increased risk of developing second primary melanoma; however, this increased risk has not been well characterized with respect to age and time from first melanoma. We hypothesized that, as a result of temporal variations in environmental exposure, genetic susceptibility, and impaired immune competence, the incidence of second primary melanoma varies significantly with respect to age and time. A review of our prospective melanoma data base, containing records for 8928 patients, was undertaken to identify patients with American Joint Committee on Cancer stage I and II cutaneous melanoma, who were treated from 1971 to 1998. Second primary melanoma was identified in 113 (3.4%) of 3310 patients with American Joint Committee on Cancer stage I and II cutaneous melanoma. In 11 patients (0.3%), the second melanoma was identified within 2 months of the initial tumor; the remaining 102 patients had a metachronous lesion. The incidence rate of second primary melanoma was 325 per 100,000. The standardized incidence ratio, defined as the ratio of the number of observed second melanomas to the number of expected melanoma cases, was 25.6. The 5- and 10-year risk of developing a second melanoma was 2.8% and 3.6%, respectively. Both the annual risk of developing a second melanoma and the standardized incidence ratio were elevated in younger patients (ages 15-39 years) and in older patients (ages 65-79 years). Patients with cutaneous melanoma are at very high risk for development of second primary melanoma. This risk approximates 0.5% per year for the first 5 years of follow-up. Patients aged 15-39 and patients aged 65-79 have a particularly high incidence of second melanoma, suggesting different causes for the development of second primaries. All patients with melanoma should undergo careful surveillance for second melanomas in addition to routine screening for recurrence.