Sex disparities in cancer mortality and survival.

BACKGROUND

Previous research has noted higher cancer mortality rates and lower survival among males than females. However, systematic comparisons of these two metrics by sex have been limited.

METHODS

We extracted U.S. vital rates and survival data from the Surveillance, Epidemiology and End Results Database for 36 cancers by sex and age for the period 1977 to 2006. We compared sex-specific mortality rates and examined male-to-female mortality rate ratios (MRR). We also extracted case data which included age and date of diagnosis, sex, primary cancer site, tumor stage and grade, survival time, vital status, and cause of death. Relative cancer-specific HRs for death in the 5-year period following diagnosis were estimated with Cox proportional hazards models, adjusted for covariates.

RESULTS

For the vast majority of cancers, age-adjusted mortality rates were higher among males than females with the highest male-to-female MRR for lip (5.51), larynx (5.37), hypopharynx (4.47), esophagus (4.08), and urinary bladder (3.36). Cancer-specific survival was, for most cancers, worse for males than females, but such disparities were drastically less than corresponding MRRs [e.g., lip (HR = 0.93), larynx (HR = 1.09), hypopharynx (HR = 0.98), esophagus (HR = 1.05), and urinary bladder (HR = 0.83)].

CONCLUSIONS

Male-to-female MRRs differed markedly while cancer survival disparities were much less pronounced. This suggests that sex-related cancer disparities are more strongly related to etiology than prognosis.

IMPACT

Future analytic studies should attempt to understand causes of observed sex disparities in cancer.