The epidemiologist's perspective
- SW Duffy1
© BioMed Central 2002
Published: 1 July 2002
By examining the stage-shifts in mammographic screening trials, and the fatality rates by stage, one can derive estimates of which cancers detected at screening save most lives. We partition the mortality avoided by screening into deaths prevented by stage-shifting from invasive carcinoma of stage II or worse to invasive carcinoma of stage I, and those prevented by shifting from invasive carcinoma of stage I to ductal carcinoma in situ. Using data from the Swedish Two-County Study, we find that around 5% of the deaths avoided in the invited arm were prevented by detection of ductal carcinoma in situ and around 65% by stage-shifting from stage II+ to stage I within the invasive carcinomas. Further results by tumour type and grade are presented to quantify the size and timing of the future mortality reduction from the cancers diagnosed.