Background:
Reported sex differences in cancer occurrence and survival highlight potentials for improvement in prevention and treatment strategies. To realise this potential, a better understanding of the mechanisms underlying these disparities is needed. We assessed differences in incidence and survival between sexes for non-sex-specific cancers and explored the contribution of socioeconomic factors and comorbidity to these differences.
Methods:
We identified all individuals living in Denmark from 2004 to 2020. Information on cancer diagnosis was obtained from the nationwide Danish Cancer Registry. Differences in sex-specific incidence rates and relative survival were assessed for 35 cancers, individually and combined by means of incidence rate ratios (IRRs) and excess mortality ratios (EMRs) using Poisson regression models adjusted for age and year of diagnosis. For each cancer, we explored modification of associations between sex and death by cohabitation status, education level, and comorbidity on multiplicative and additive scales.
Results:
We followed 7,339,667 individuals for a total of 99,832,998 person-years, during which 355,339 were registered with a primary malignancy (197,375 males, 157,964 females). Males had 52% higher risk of developing any of the studied cancers and 10% higher mortality than females. Incidence rates were statistically significantly increased for 24 cancers and excess mortality for 16 cancers in males. We estimated that one in six incident cancers and one in five cancer deaths could have been avoided in males if they experienced the same incidence and survival rates as females. IRRs and EMRs were particularly elevated among males living alone, especially for alcohol and smoking-related cancers.
Conclusion and clinical implications:
There is a need to address sex differences in cancer research, and to translate findings into interventions targeting sex equality in both preventive as well as in early diagnostics, cancer treatment, and supportive care in cancer.