Bias in breast cancer research in the screening era

Abstract

Screening aims to detect breast cancer at an earlier stage than would occur if symptoms developed. The characteristics of breast cancer that are detectable at screening depend on both the physical properties of the screening test and specific anatomical features of breast cancer. As a result, breast cancer detected by screening is a select subset of all breast cancer existing in the population. Therefore, biomedical, clinical and epidemiological research into breast cancer using populations with access to screening can result in major bias. The biases, with examples, are explained.

Carcinoma Lobular Invasor Bilateral: relato de caso

“…Pacientes portadoras de CLI podem ser tratadas adequadamente com cirurgia conservadora, tudo depende do caso, é por isso que as pacientes devem ser individualmente avaliadas: para que o tratamento indicado seja o mais apropriado ao caso 2 . A triagem tem como objetivo detectar o câncer de mama em um estágio anterior do que ocorreria se os sintomas se desenvolvam 10 .…”

Screening Mammography

“…They explained with examples that a variety of biases lead to overestimates of the benefit and underestimates of the harms of screening (30).…”

Effect of implementation of the mass breast cancer screening programme in older women in the Netherlands: population based study

“…[25][26][27] These contradictory results can be explained by the fact that studying survival rates as an indicator for the effect of screening programmes is notoriously difficult because of the several forms of bias present in such studies. 16 Firstly, as a result of increased detection of early stage tumours, possible favourable effects of screening on survival are generally overestimated since a large percentage of early stage screen detected tumours are indolent and have an excellent prognosis. 17 Consequently, interval detected tumours are generally more aggressive.…”

“…Furthermore, comorbidity and poor physical functioning in older women lead to poor attendance to the screening programme and can therefore result in biased outcomes of these observational studies. 16 A more appropriate way to investigate the efficacy of a screening programme in population based data would be to investigate the incidence rates of advanced stage cancers after implementation of a screening programme. 17 If a screening programme is effective, it can be expected that the incidence of advanced stage cancer decreases, while the incidence of early stage breast cancer increases.…”