The relative contributions of screen-detected in situ and invasive XXXX in reducing mortality from the disease.

@entity3821 @entity0 @entity5 @entity10365 @entity189 @entity204
We aimed to quantify the benefits of detecting @entity3821 ( @entity3821 ) and of downwards stage-shifting within invasive @entity5 in mammographic screening. Using data from the Swedish Two-County Trial of @entity0 screening, we examined the 20-year death rates from invasive @entity5 of stage II or worse, invasive @entity5 of stage I and @entity3821 . We then used these rates and their respective incidences in invited (active study population, ASP) and control (passive study population, @entity10365 ) arms of the trial, to estimate the numbers of @entity204 avoided by downward stage-shifting the larger stage II or worse @entity5 to stage I and the stage I cancers to @entity3821 . We also studied the association between the mortality reduction achieved and the proportion of @entity3821 cases detected in the randomised trials of @entity0 screening. In the Swedish Two County Trial, 141 @entity0 @entity204 were avoided in the ASP compared with the @entity10365 at approximately 20 years of follow-up. Of these, 65% (91/141) were avoided as a result of stage-shifting from invasive stage II or worse to invasive stage I, and 5% (7/141) as a result of stage-shifting from invasive stage I to @entity3821 . If we assumed that 10% of stage II or worse @entity5 avoided were shifted not to stage I, but to @entity3821 , the estimated number of @entity204 prevented by shifting from invasive disease to in situ was 17, which is 12% of all @entity204 prevented. When the results of all the randomised trials of @entity0 screening were reviewed, there was no clear association between the percentage of @entity3821 cases diagnosed and the observed mortality reduction. We conclude that compared with downward stage-shifting of invasive @entity5 , detection of @entity3821 plays a small part in saving lives from @entity0 . Treatment decisions in @entity3821 , as in @entity189 , should take full account of histopathological, clinical and radiological attributes of the @entity5 .
