There are important differences between disparities in survival and disparities in mortality
James Scanlan, James P. Scanlan, Attorney at Law
16 October 2013
The article by Yu [1] reflects a problem with discussion of demographic differences in cancer outcomes that is as common today as when the article was written. The article purports to be analyzing socioeconomic disparities in mortality but, as with most articles that make reference to survival disparities in their titles, it in fact analyzes differences in mortality.
Where there are differences in survival there will of course be differences in mortality. And where, as in the Yu article, factors explain disparities in mortality, they will also explain disparities in survival.
But in many contexts whether one examines relative differences in mortality or relative differences in survival will have important implications given the pattern whereby the rarer an outcome, the greater tends to be the relative difference in experiencing it and the smaller tends to be the relative difference in avoiding it. Among the implications of such pattern with respect to cancer outcomes, as survival generally increases relative differences in survival will tend to decrease while relative differences in mortality will tend to increase; more survivable cancers will tend to show smaller relative differences in survival, but larger relative differences in mortality, than less survivable cancers. Further, among groups with generally high survival rates such as the young, relative (racial, socioeconomic, etc.) differences in survival will tend to be smaller while relative differences in mortality will tend to be larger, than among groups with generally low survival rates.[2-4]
So analyses of disparities in cancer outcomes should be clear on which outcome is actually being examined. More important, whichever outcome is being examined, such analyses should recognize the implications of the prevalence of an outcome on the measure being employed and interpret results in light of those implications.
References:
1. Yu XQ. Socioeconomic disparities in breast cancer survival: relation to stage at diagnosis, treatment and race. BMC Cancer 2009, 9:364: doi:10.1186/1471-2407-9-364: http://www.biomedcentral.com/1471-2407/9/364
2. Mortality and Survival Page of jpscanlan.com: http://jpscanlan.com/mortalityandsurvival2.html
3. Scanlan JP. Race and mortality. Society 2000;37(2):19-35: (reprinted in Current 2000 (Feb)):
http://www.jpscanlan.com/images/Race_and_Mortality.pdf
4. Life Tables Illustrations subpage of Scanlan¿s Rule page of jpscanlan.com: http://jpscanlan.com/scanlansrule/lifetableillustrations.html
There are important differences between disparities in survival and disparities in mortality
16 October 2013
The article by Yu [1] reflects a problem with discussion of demographic differences in cancer outcomes that is as common today as when the article was written. The article purports to be analyzing socioeconomic disparities in mortality but, as with most articles that make reference to survival disparities in their titles, it in fact analyzes differences in mortality.
Where there are differences in survival there will of course be differences in mortality. And where, as in the Yu article, factors explain disparities in mortality, they will also explain disparities in survival.
But in many contexts whether one examines relative differences in mortality or relative differences in survival will have important implications given the pattern whereby the rarer an outcome, the greater tends to be the relative difference in experiencing it and the smaller tends to be the relative difference in avoiding it. Among the implications of such pattern with respect to cancer outcomes, as survival generally increases relative differences in survival will tend to decrease while relative differences in mortality will tend to increase; more survivable cancers will tend to show smaller relative differences in survival, but larger relative differences in mortality, than less survivable cancers. Further, among groups with generally high survival rates such as the young, relative (racial, socioeconomic, etc.) differences in survival will tend to be smaller while relative differences in mortality will tend to be larger, than among groups with generally low survival rates.[2-4]
So analyses of disparities in cancer outcomes should be clear on which outcome is actually being examined. More important, whichever outcome is being examined, such analyses should recognize the implications of the prevalence of an outcome on the measure being employed and interpret results in light of those implications.
References:
1. Yu XQ. Socioeconomic disparities in breast cancer survival: relation to stage at diagnosis, treatment and race. BMC Cancer 2009, 9:364: doi:10.1186/1471-2407-9-364: http://www.biomedcentral.com/1471-2407/9/364
2. Mortality and Survival Page of jpscanlan.com: http://jpscanlan.com/mortalityandsurvival2.html
3. Scanlan JP. Race and mortality. Society 2000;37(2):19-35: (reprinted in Current 2000 (Feb)):
http://www.jpscanlan.com/images/Race_and_Mortality.pdf
4. Life Tables Illustrations subpage of Scanlan¿s Rule page of jpscanlan.com: http://jpscanlan.com/scanlansrule/lifetableillustrations.html
Competing interests
None