Original ResearchSex differences in cancer risk and survival: A Swedish cohort study

- Male sex is associated with increased risk for most cancers sites.
- The male excess risk ratio has decreased, but remains significant over time.
- The fraction of cancer explained by factors related to male sex is considerable.
- Men experience poorer survival in most cancer sites.

AimThe aim of this study is to firmly delineate temporal and age trends regarding sex discrepancies in cancer risk and survival as well as quantifying the potential gain achieved by eliminating this inequality.MethodsWe performed a population-based cohort study using data on all adult incident cancer cases (n = 872,397) recorded in the Swedish Cancer Register in 1970-2014. To assess the associations between sex and cancer risk and sex and survival, male-to-female incidence rate ratios (IRRs) and excess mortality ratios (EMRs) adjusted for age and year of diagnosis were estimated using Poisson regression.ResultsMen were at increased risk for 34 of 39 and had poorer prognosis for 27 of 39 cancers. Women were at increased risk for 5 of 39 and had significantly poorer survival for 2 of 39 cancers. IRRs among male predominant sites ranged from 1.05; 95% confidence interval (CI), 1.03--1.1 (lung adenocarcinoma) to 8.0; 95% CI, 7.5-8.5 (larynx). EMRs among sites with male survival disadvantage ranged from 1.1; 95% CI, 1.03-1.1 (colon) to 2.1; 95% CI, 1.5--2.8 (well-differentiated thyroid).ConclusionMale sex is associated with increased risk and poorer survival for most cancer sites. Identifying and eliminating factors driving the observed sex differences may reduce the global cancer burden.