Reduced disease-specific survival following a diagnosis of multiple primary cutaneous malignant melanomas-a nationwide, population-based study.

Outcome data comparing patients with multiple primary invasive cutaneous malignant melanomas (MPMs) to single primary invasive cutaneous malignant melanomas (SPMs) show conflicting results. We have analyzed differences in disease-specific survival between these patients in a nationwide population-based setting. From the Swedish Melanoma Register, 27,235 patients were identified with a first invasive cutaneous malignant melanoma (CMM) between 1990 and 2007, followed-up through 2013. Of these, 700 patients developed MPMs. Cox proportional hazard regression was used for adjusted cause-specific hazard ratios (HRs). An interval of ≤5 years between CMM diagnoses was significantly correlated to a decreased CMM-specific survival in Stage I-II MPM- vs. SPM-patients (HR 1.32; 95% CI 1.04-1.67; p = 0.02). MPM-patients with longer time interval between diagnoses experienced similar risk of CMM-death as SPM-patients. The risk of CMM-death increased by almost 50% above the expected outcome according to stage of the index CMM by the diagnosis of a second CMM (HR 1.48; 95% CI 1.19-1.85; p < 0.001). MPM vs. SPM-patients had a worse outcome (HR 1.38; 95% CI 1.05-1.83; p = 0.001). This emphasizes the importance of prevention efforts in SPM-patients to decrease the risk of subsequent CMMs and has implications for more vigilant follow-up in MPM-patients.