Sex differences in cancer incidence and survival: a Danish nationwide population-based study assessing 35 cancer sites

BACKGROUND: Sex differences in cancer incidence and survival have been documented, but underlying mechanisms remain unclear. We examined sex differences in incidence and survival for non-sex-specific cancers and the role of socioeconomic factors and comorbidity. METHODS: All individuals living in Denmark from 2004-2020 were included. Incidence rate ratios (IRRs) and excess mortality ratios (EMRs) for 35 cancers were estimated using Poisson regression adjusted for age and year. Modification of associations between sex and death by cohabitation, education and comorbidity was assessed. RESULTS: A total of 7,339,667 individuals were followed for 99,832,998 person-years, during which 355,339 were registered with a primary malignancy (197,375 males, 157,964 females). Males had a 52% higher risk of cancer and upon cancer diagnosis 10% higher mortality than females. IRRs were elevated (with confidence intervals excluding the null) for 24 cancers and EMRs for 16 cancers in males. One in six cancers and one in five cancer deaths in males could have been avoided if male rates matched female rates. Disparities were greatest among males living alone, particularly for alcohol- and smoking-related cancers. CONCLUSION: Sex differences in cancer must be addressed and translated into interventions that promote equality between sexes, specifically focusing on socioeconomically vulnerable males.