Predicting the stage shift as a result of breast cancer screening in low- and middle-income countries: a proof of concept.
OBJECTIVE
To provide proof of concept for a simple model to estimate the stage shift as a result of breast cancer screening in low- and middle-income countries (LMICs). Stage shift is an essential early detection indicator and an important proxy for the performance and possible further impact of screening programmes. Our model could help LIMCs to choose appropriate control strategies.


METHODS
We assessed our model concept in three steps. First, we calculated the proportional performance rates (i.e. index number Z) based on 16 screening rounds of the Nijmegen Screening Program (384,884 screened women). Second, we used linear regression to assess the association between Z and the amount of stage shift observed in the programme. Third, we hypothesized how Z could be used to estimate the stage shift as a result of breast cancer screening in LMICs.


RESULTS
Stage shifts can be estimated by the proportional performance rates (Zs) using linear regression. Zs calculated for each screening round are highly associated with the observed stage shifts in the Nijmegen Screening Program (Pearson's R: 0.798, R square: 0.637).


CONCLUSIONS
Our model can predict the stage shifts in the Nijmegen Screening Program, and could be applied to settings with different characteristics, although it should not be straightforwardly used to estimate the impact on mortality. Further research should investigate the extrapolation of our model to other settings. As stage shift is an essential screening performance indicator, our model could provide important information on the performance of breast cancer screening programmes that LMICs consider implementing.
['Zelle|Sten G|SG|', 'Baltussen|Rob|R|', 'Otten|Johannes D M|JD|', 'Heijnsdijk|Eveline A M|EA|', 'van Schoor|Guido|G|', 'Broeders|Mireille J M|MJ|']
D000328:Adult D000368:Aged D000369:Aged, 80 and over D001943:Breast Neoplasms D003906:Developing Countries D055088:Early Detection of Cancer D005260:Female D006801:Humans D016014:Linear Models D008403:Mass Screening D008875:Middle Aged D008954:Models, Biological D011203:Poverty D055815:Young Adult
breast cancer screening model Breast cancer control CBE screening developing countries stage distribution validation