Predictors of primary cutaneous melanoma stage at diagnosis: observations from Alberta’s Tomorrow Project

: Melanoma is the leading cause of skin cancer deaths in Canada, with increasing average annual percent change in age-standardized incidence rates of 2.0% between 1984 and 2017. Identifying novel or corroborating previously known factors associated with early stage at diagnosis could reduce mortality from melanoma. This study utilized data from adults initially aged 35–69 years that enrolled in Alberta's Tomorrow Project between 2000 and 2008 who were confirmed to have developed primary cutaneous melanoma. Of the 62 participants who developed cutaneous melanoma by 2018 with known stage and lifestyle information, 42 patients were diagnosed at stage I (67.74%), 11 patients were at stage II (17.74%), and 9 patients at stages III and IV (14.52%). Individual factors associated with being diagnosed with stage I disease versus higher stages based on Fisher's exact test included being married or common-law (P=0.06), having an annual household income between $50,000–100,000 (P=0.01), and spending more than 1 hour in the sun 11 am–4 pm per day during the past June through August (P=0.04). In the final multivariable logistic regression model, higher annual household incomes were protective against higher stages of melanoma [>$100,000 versus <$50,000: odds ratio (OR) =0.069, 95% confidence interval (CI): 0.006–0.733, P=0.02]. When the number of hours spent in the sun between 11 am–4 pm per day during the past summer was more than 1 hour, this factor was also protective against higher stages of melanoma (1–2 versus <1 hour: OR =0.153, 95% CI: 0.024–0.976, P=0.04; and >2 versus <1 hour: OR =0.235, 95% CI: 0.048–1.156, P=0.07). Increasing occupational physical activity was the only identified factor associated with a later stage at diagnosis (OR =1.017, 95% CI: 1.003, 1.031, P=0.02). Establishing epidemiologic risk factors for delayed detection of melanoma may inform targeted interventions that can ultimately lead to improved survival.