Distribution of subsequent primary invasive melanomas following a first primary invasive or in situ melanoma Queensland, Australia, 1982-2010.

Abstract

Melanoma survivors are known to have a highly elevated risk of subsequent primary melanomas. To determine the relative risk of subsequent primary invasive melanomas following a first primary invasive or in situ melanoma, with a focus on body site. A retrospective cohort study was conducted using population-based administrative data for melanoma diagnoses collected by the Queensland Cancer Registry, Queensland, Australia. Deidentified records of all cases of melanoma among Queensland residents during the period 1982-2005 were obtained and reviewed to December 31, 2010. There were 39,668 eligible cases of first primary invasive melanoma and 22,845 cases of first primary in situ melanoma. Standardized incidence ratios (SIRs), a proxy measure for relative risk, were calculated by dividing the observed number of subsequent primary invasive melanomas by the product of the strata-specific incidence rates that occurred in the general population and the cumulative time at risk for the cohort. Synchronous subsequent melanomas (diagnosed within 60 days of the first primary melanoma) were excluded. Differences between SIRs were assessed using multivariate negative binomial regression adjusted for sex, age group, time to second diagnosis, and body site and expressed in terms of adjusted SIR ratios with corresponding 95% CIs. There were 5358 subsequent primary invasive melanomas diagnosed, resulting in SIRs of 5.42 (95% CI, 5.23-5.61) and 4.59 (4.37-4.82) for persons with a first primary invasive or in situ melanoma, respectively. The SIRs remained elevated throughout the follow-up period. In general, subsequent primary invasive melanomas were more likely to occur at the same body site as the initial invasive or in situ melanoma. The largest relative risk was for females with a first primary invasive melanoma on the head followed by a subsequent primary invasive melanoma also on the head (SIR, 13.32; 95% CI, 10.28-16.98). Melanoma survivors require ongoing surveillance, with particular attention required for the body site of the initial lesion. Clinical practice guidelines have recognized the importance of monitoring for people with invasive melanoma; the results of the present study highlight the need for similar levels of supervision for those with a diagnosis of in situ melanoma.