Similar survival of patients with multiple versus single primary melanomas based on Utah Surveillance, Epidemiology, and End Results data (1973-2011)

Background: Survival data are mixed comparing patients with multiple primary melanomas (MPM) to those with single primary melanomas (SPM). Objectives: We compared MPM versus SPM patient survival using a matching method that avoids potential biases associated with other analytic approaches. Methods: Records of 14,138 individuals obtained from the Surveillance, Epidemiology, and End Results registry of all melanomas diagnosed or treated in Utah between 1973 and 2011 were reviewed. A single matched control patient was selected randomly from the SPM cohort for each MPM patient, with the restriction that they survived at least as long as the interval between the first and second diagnoses for the matched MPM patient. Results: Survival curves (n=887 for both MPM and SPM groups) without covariates showed a significant survival disadvantage for MPM patients (chi-squared 39.29, P<.001). However, a multivariate Cox proportional hazards model showed no significant survival difference (hazard ratio 1.07, P=.55). Restricting the multivariate analysis to invasive melanomas also showed no significant survival difference (hazard ratio 0.99, P=.96). Limitations: Breslow depth, ulceration status, and specific cause of death were not available for all patients. Conclusions: Patients with MPM had similar survival times as patients with SPM.