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BackgroundMetformin use has been associated with improved survival in patients with different types of cancer, but research regarding the effect of metformin on cutaneous melanoma (CM) survival is sparse and inconclusive.ObjectivesTo investigate the association between metformin use and survival among patients with CM and diabetes.MethodsAll adult patients with a primary invasive CM between 2007 and 2014 were identified in the Swedish Melanoma Registry and followed until death, or end of follow-up on 31 December 2017 in this population-based cohort study. Patients with both CM and type 2 diabetes mellitus were assessed further. Overall survival (OS) and melanoma-specific survival (MSS) were the primary endpoints. Cox proportional hazard models estimating crude and adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were used comparing peridiagnostic use vs. nonuse of metformin. Dose response was evaluated based on defined daily doses.ResultsAmong a total of 23 507 patients, 1162 patients with CM and type 2 diabetes mellitus were included in the final cohort, with a median follow-up time of 4.1 years (interquartile range 2.4–6.1). Peridiagnostic metformin use was associated with a significantly decreased risk of death by any cause (HR 0.68, 95% CI 0.57–0.81). Cumulative pre- and postdiagnostic metformin use was also associated with improved OS: the HR for prediagnostic use was 0.90 (95% CI 0.86–0.95) for every 6 months of use and the HR for postdiagnostic use ranged from 0.98 (95% CI 0.97–0.98) for 0–6 months to 0.59 (0.49–0.70) for 24–30 months of use. No association was found for metformin use and MSS.ConclusionsMetformin use was associated with improved OS in patients with CM and diabetes regardless of timing (pre-, post- or peridiagnostic use) and followed a dose–response pattern. However, further research regarding the underlying mechanisms is warranted.

Background Over the past decades, many regions have experienced a steady increase in the incidence of cutaneous melanoma. Here, we report on incidence trends for subsequent primary melanoma. Methods In this nationwide population-based study, patients diagnosed with a first primary cutaneous melanoma reported to the Swedish Cancer Registry were followed for up to 10 years for a diagnosis of subsequent primary melanoma. Patients were grouped with patients diagnosed with first melanoma in the same decade (1960s, 1970s, 1980s, 1990s, and 2000s, respectively). Frequencies, incidence rates (IRs), standardized incidence ratios (SIRs), and 95% confidence intervals (CIs) for second melanomas were calculated. All tests of statistical significance were 2-sided. Results Of patients with melanoma, 54 884 were included and 2469 were diagnosed, within 10 years, with subsequent melanomas. Over the 5 decades, there was a statistically significant steady increase in the frequency, IR, and SIR for second primary melanoma. For example, in the 1960s cohort, less than 1% (IR = 1.0, 95% CI = 0.5 to 1.7, and IR = 1.1, 95% CI = 0.5 to 1.9 per 1000 person-years in women and men, respectively) had second primary melanoma, and this rose to 6.4% (IR = 7.5, 95% CI = 6.8 to 8.3, per 1000 person-years) in the women and 7.9% (IR = 10.3, 95% CI = 9.3 to 11.2, per 1000 person-years) in the men in the 2000s cohort. This rise was seen independent of age, sex, invasiveness, or site of the melanoma. Further, in patients diagnosed with a second melanoma, the frequency of those having more than 2 melanomas increased statistically significantly and was 0.0% in the 1960s and rose to 18.0% in the 2000s (P < .001). Conclusions This is the first study to evaluate and report on a rising trend for subsequent primary melanoma. Additional primary melanomas worsen the patients’ survival, and precautions are needed to turn this steep upgoing trend.

Background Survival and prognostic factors for thin melanomas have been studied relatively little in population-based settings. This patient group accounts for the majority of melanomas diagnosed i ...

Background Melanoma risk is related to sun exposure; we have investigated risk variation by tumour site and latitude. Methods We performed a pooled analysis of 15 case-control studies (5700 melanoma cases and 7216 controls), correlating patterns of sun exposure, sunburn and solar keratoses (three studies) with melanoma risk. Pooled odds ratios (pORs) and 95% Bayesian confidence intervals (CIs) were estimated using Bayesian unconditional polytomous logistic random-coefficients models. Results Recreational sun exposure was a risk factor for melanoma on the trunk (pOR 1.7; 95% CI: 1.4-2.2) and limbs (pOR 1.4; 95% CI: 1.1-1.7), but not head and neck (pOR 1.1; 95% CI: 0.8-1.4), across latitudes. Occupational sun exposure was associated with risk of melanoma on the head and neck at low latitudes (pOR 1.7; 95% CI: 1.0-3.0). Total sun exposure was associated with increased risk of melanoma on the limbs at low latitudes (pOR 1.5; 95% CI: 1.0-2.2), but not at other body sites or other latitudes. The pORs for sunburn in childhood were 1.5 (95% CI: 1.3-1.7), 1.5 (95% CI: 1.3-1.7) and 1.4 (95% CI: 1.1-1.7) for melanoma on the trunk, limbs, and head and neck, respectively, showing little variation across latitudes. The presence of head and neck solar keratoses was associated with increased risk of melanoma on the head and neck (pOR 4.0; 95% CI: 1.7-9.1) and limbs (pOR 4.0; 95% CI: 1.9-8.4). Conclusion Melanoma risk at different body sites is associated with different amounts and patterns of sun exposure. Recreational sun exposure and sunburn are strong predictors of melanoma at all latitudes, whereas measures of occupational and total sun exposure appear to predict melanoma predominately at low latitudes. Keywords Melanoma, recreational sun exposure, occupational sun exposure, total sun exposure, sunburn, solar keratoses

In a population-based, matched case-control study from the South Swedish Health Care Region, which has the highest risk for melanoma in Sweden, the relation between the use of sunbeds or sunlamps and malignant melanoma was investigated. Between July 1, 1988, and June 30, 1990, a total of 400 melanoma patients and 640 healthy controls aged 15-75 years answered a comprehensive questionnaire containing different epidemiologic variables. Questions regarding the use of sunbeds or sunlamps were included. The odds ratio for developing malignant melanoma after ever having used sunbeds or sunlamps was 1.3. Considering all age groups, the odds ratio was significantly elevated after exposure more than 10 times a year to sunbeds or sunlamps (odds ratio (OR) = 1.8). When the study was restricted to patients and controls younger than age 30 years because the use of tanning devices is much more common among young persons, the odds ratio was higher (OR = 7.7 for more than 10 times a year vs. none). These findings were independent of constitutional factors and factors regarding sun exposure. A dose-response relation was evident. Furthermore, among melanoma patients in this young age group, the ratio of females to males was significantly higher than in older patients. When different melanoma presentation sites were considered, only lesions of the trunk were significantly associated with sunbed or sunlamp use (OR = 4.2 for more than 10 times a year vs. none).