How much of the deprivation gap in cancer survival can be explained by variation in stage at diagnosis: an example from breast cancer in the East of England.

Socioeconomic differences in cancer patient survival exist in many countries and across cancer sites. In our article, we estimated the number of deaths in women with breast cancer that could be avoided within 5 years from diagnosis if it were possible to eliminate socioeconomic differences in stage at diagnosis. We analysed data on East of England women with breast cancer (2006-2010). We estimated survival for different stage-age-deprivation strata using both the observed and a hypothetical stage distribution (assuming all women acquired the stage distribution of the most affluent women). Data were analysed on 20,738 women with complete stage information (92%). Affluent women were less likely to be diagnosed in advanced stage. Relative survival decreased with increasing level of deprivation. Eliminating differences in stage at diagnosis could be expected to nearly eliminate differences in relative survival for women in deprivation groups 3 and 4, but would only approximately halve the difference in relative survival for women in the most deprived group (5). This means, for a typical cohort of women diagnosed in a calendar year with breast cancer, eliminating deprivation differences in stage at diagnosis would prevent ∼40 deaths in the East of England from occurring within 5 years from diagnosis. Using appropriate weighting we estimated the respective number of avoidable deaths for the whole of England to be ∼450. The findings suggest that policies aimed at reducing inequalities in stage at diagnosis between women with breast cancer are important to reduce inequalities in breast cancer survival.

Should relative survival be used with lung cancer data?

BACKGROUND: Under certain assumptions, relative survival is a measure of net survival based on estimating the excess mortality in a study population when compared with the general population. Background mortality estimates are usually taken from national life tables that are broken down by age, sex and calendar year. A fundamental assumption of relative survival methods is that if a patient did not have the disease of interest then their probability of survival would be comparable to that of the general population. It is argued, as most lung cancer patients are smokers and therefore carry a higher risk of smoking-related mortalities, that they are not comparable to a population where the majority are likely to be non-smokers. METHODS: We use data from the Finnish Cancer Registry to assess the impact that the non-comparability assumption has on the estimates of relative survival through the use of a sensitivity analysis. RESULTS: Under realistic estimates of increased all-cause mortality for smokers compared with non-smokers, the bias in the estimates of relative survival caused by the non-comparability assumption is negligible. CONCLUSION: Although the assumption of comparability underlying the relative survival method may not be reasonable, it does not have a concerning impact on the estimates of relative survival, as most lung cancer patients die within the first 2 years following diagnosis. This should serve to reassure critics of the use of relative survival when applied to lung cancer data.