Abstract
BACKGROUND: Cancer has become the leading diabetes-related cause of death in high-income countries, and more knowledge is needed to clarify the impact of diabetes on site-specific cancers. The purpose of this study is to assess the association between diabetes and malignant melanoma by conducting a comprehensive systematic review and meta-analysis. METHODS: Using predefined eligibility criteria, PubMed, The Cochrane Library and Web of Science were systematically searched up to February 22, 2023. Exposure was defined as diabetes or type 2 diabetes and the outcomes were defined as melanoma incidence, melanoma stage or melanoma-specific mortality. The identified articles were evaluated by two independent reviewers and quality assessment was conducted using the Newcastle-Ottawa Scale for observational studies. Meta-analyses were conducted using RevMan 5.4.1 on melanoma risk using adjusted risk estimates and on melanoma stage using a dichotomous model. RESULTS: The literature search revealed 20 studies in total eligible for inclusion, 14 for the analysis of melanoma risk, 3 for melanoma thickness and ulceration, and 4 for melanoma-specific survival. According to the meta-analyses, diabetes did not impact the risk of developing melanoma (RR:1.05, 95%CI:0.99-1.12, p = 0.10). However, type 2 diabetes was associated with more advanced melanoma stages at the time of diagnosis (Breslow-thickness > 1 mm: RR 1.35, 95%CI: 1.22-1.49, p = < 0.001) and presence of ulceration (RR 1.30, 95%CI: 1.00-1.68, p = 0.05). A meta-analysis on the association between diabetes and melanoma-specific mortality was not feasible due to diverse study designs. CONCLUSION: Our meta-analysis found no association between diabetes and the risk of developing melanoma, but diabetes was associated with increased tumour thickness and the presence of ulceration at the time of diagnosis. Further research is warranted to explore the association between diabetes melanoma stage and prognosis. TRIAL REGISTRATION: PROSPERO ID CRD42023394187.