Sex differences in cancer survival in Estonia: a population-based study

BACKGROUND: In Estonia, women have much longer life expectancy than men. The aim of this study was to examine sex differences in cancer survival in Estonia and to explore the role of age at diagnosis, stage at diagnosis and tumour subsite. METHODS: Using data from the population-based Estonian Cancer Registry, we examined the relative survival of adult patients diagnosed with nine common cancers in Estonia in 1995–2006 and followed up through 2011. Excess hazard ratios (EHR) of death associated with female gender adjusted for age, stage at diagnosis and tumour subsite were estimated. RESULTS: A total of 20 828 male and 13 166 female cases were analysed. The main data quality indicators were similar between men and women. Women had more cases with unknown extent of disease at diagnosis. Overall, the age-adjusted 5-year relative survival ratio was higher among women than men for all studied sites, but the difference was significant for cancers of mouth and pharynx (22% units), lung (5% units), skin melanoma (17% units) and kidney (8% units). The increase in survival over time was larger for women than men for cancers of mouth and pharynx, colon, rectum, kidney and skin melanoma. In multivariate analysis, women had a significantly lower EHR of death within five years after diagnosis for five of the nine cancers studied (cancers of mouth and pharynx, stomach, lung, skin melanoma and kidney). Adjustment for stage and subsite explained some, but not all of the women’s advantage. CONCLUSIONS: We found a significant female survival advantage in Estonia for cancers of mouth and pharynx, stomach, lung, kidney and skin melanoma. The differences in favour of women tended to increase over time as from the 1990s to the 2000s, survival improved more among women than among men. A large part of the women’s advantage is likely attributable to biological factors, but other factors, such as co-morbidities, treatment compliance or health behaviour, are also probable contributors to gender survival disparities in Estonia and merit further investigation. Our findings have implications for public health, early detection and cancer care in Estonia.