1330Is Prognosis Worse for People with Multiple Versus Single Primary Melanoma?

Abstract

Abstract Background Patients with a primary melanoma may develop more than one in their lifetime. It is unclear whether mortality is worse after diagnosis of multiple primary melanoma (MPM) compared with single primary melanoma (SPM). Methods We analysed data from a population-based cohort of 3,869 patients diagnosed with primary in situ or invasive cutaneous melanoma in New South Wales, Australia in 2006-07 and followed up until 2018 (median 11.9 years) using linked mortality and cancer registry data. We compared overall mortality and melanoma-specific mortality for patients with SPM versus MPM, adjusting for other clinico-pathological prognostic indicators, using Cox proportional hazard models. The primary analysis was based on pathological features from the thickest tumour for MPM patients, however sensitivity analyses were performed using the first and last primary melanoma. Results The cohort consisted of 3,869 patients (2,929 SPM and 940 MPM) and 5,504 melanoma lesions (including 2,575 lesions from MPM patients). The primary multivariable analysis showed MPM was associated with lower mortality from all causes and melanoma compared with SPM with a hazard ratio of 0.62 (95% CI: 0.54-0.71, p < 0.001) and 0.37 (95% CI: 0.32-0.43, p < 0.001) respectively. These findings were also supported by the sensitivity analyses. Conclusions The diagnosis of MPM does not worsen mortality compared to a SPM, in fact it was associated with improved survival. This finding might be related to skin examination behaviours, biological or clinical factors. Key messages MPM patients have a better prognosis than SPM patients.