Sex differences in lymphoma incidence and mortality by subtype: A population-based study

It is well established that the male sex is associated with increased risk for, as well as poorer survival of, most cancers. A similar pattern has been described in lymphomas but has not yet been comprehensively assessed. In this nationwide population-based cohort study, we used the Swedish Lymphoma Register to investigate sex differences in lymphoma subtype incidence and excess mortality in adults (age 18-99) diagnosed in 2000-2019. Male-to-female incidence rate ratios (IRRs) and excess mortality ratios (EMRs) adjusted for age and calendar year were predicted using Poisson regression. We identified 36 795 lymphoma cases, 20 738 (56.4%) in men and 16 057 (43.6%) in women. Men were at significantly higher risk of 14 out of 16 lymphoma subtypes with IRRs ranging from 1.15 (95% confidence interval [CI] 1.09-1.22) in follicular lymphoma to 5.95 (95% CI 4.89-7.24) in hairy cell leukemia. EMRs >1 were seen in 13 out of 16 lymphoma subtypes indicating higher mortality in men, although only statistically significant for classical Hodgkin lymphoma 1.26 (95% CI 1.04-1.54), aggressive lymphoma not otherwise specified 1.29 (95% CI 1.08-1.55), and small lymphocytic lymphoma 1.52 (95% CI 1.11-2.07). A corresponding analysis using data from the Danish Lymphoma Register was performed with comparable results. In conclusion, we demonstrate a significantly higher incidence and trend toward higher mortality in men for most lymphoma subtypes. Future studies with large patient material that include detailed clinicopathological prognostic factors are warranted to further delineate and explain sex differences in lymphoma survival to enable optimal management of lymphoma patients regardless of sex.