Explaining the difference in prognosis between screen-detected and symptomatic breast cancers.

Background: We analysed 10-year survival data in 19,411 women aged 50-64 years diagnosed with invasive breast cancer in the West Midlands region of the United Kingdom. The aim was to estimate the survival advantage seen in cases that were screen detected compared with those diagnosed symptomatically and attribute this to shifts in prognostic variables or survival differences specific to prognostic categories.

Methods: We studied tumour size, histological grade and the Nottingham Prognostic Index in very narrow categories and investigated the distribution of these prognostic factors within screen-detected and symptomatic tumours.

Prognosis and pathology of screen-detected carcinomas: how different are they?

Background: It has been observed that screen-detected breast cancers have a better prognosis than symptomatic tumors, even after taking pathological tumor attributes into account. This has led to the hypothesis that screen-detected tumors are substantially biologically different from symptomatic cancers.

Methods: The pathology and survival by detection mode was investigated in 21,382 breast cancers diagnosed in women aged 50-64 years in the West Midlands, United Kingdom, between 1988 and 2004.

Screening histories of invasive breast cancers diagnosed 1989-2006 in the West Midlands, UK: variation with time and impact on 10-year survival.

Objectives: To examine variations in screening status category with time for 20,862 invasive breast cancers diagnosed in the West Midlands between 1989 and 2006, and to provide 10-year relative survival rates for each category.

Method: Population-based breast screening was introduced in the West Midlands from 1988. Primary invasive breast cancers diagnosed from 1 April 1989 to 31 March 2006 in women eligible for breast screening were identified from the West Midlands Cancer Intelligence Unit's cancer registration database.

Population estimates of survival in women with screen-detected and symptomatic breast cancer taking account of lead time and length bias.

Background: Evidence of the impact of breast screening is limited by biases inherent in non-randomised studies and often by lack of complete population data. We address this by estimating the effect of screen detection on cause-specific fatality in breast cancer, corrected for all potential biases, using population cancer registry data.

Methods: Subjects (N = 26,766) comprised all breast cancers notified to the West Midlands Cancer Intelligence Unit and diagnosed in women aged 50-74, from 1988 to 2004.

Correcting for lead time and length bias in estimating the effect of screen detection on cancer survival.

Determination of survival time among persons with screen-detected cancer is subject to lead time and length biases. The authors propose a simple correction for lead time, assuming an exponential distribution of the preclinical screen-detectable period. Assuming two latent categories of tumors, one of which is more prone to screen detection and correspondingly less prone to death from the cancer in question, the authors have developed a strategy of sensitivity analysis for various magnitudes of length bias.