Effectiveness of service screening: a case-control study to assess breast cancer mortality reduction

Increasingly strong reduction in breast cancer mortality due to screening

BACKGROUND

Favourable outcomes of breast cancer screening trials in the 1970s and 1980s resulted in the launch of population-based service screening programmes in many Western countries. We investigated whether improvements in mammography and treatment modalities have had an influence on the effectiveness of breast cancer screening from 1975 to 2008.

METHODS

In Nijmegen, the Netherlands, 55,529 women received an invitation for screening between 1975 and 2008. We designed a case-referent study to evaluate the impact of mammographic screening on breast cancer mortality over time from 1975 to 2008. A total number of 282 breast cancer deaths were identified, and 1410 referents aged 50-69 were sampled from the population invited for screening. We estimated the effectiveness by calculating the odds ratio (OR) indicating the breast cancer death rate for screened vs unscreened women.

RESULTS

The breast cancer death rate in the screened group over the complete period was 35% lower than in the unscreened group (OR=0.65; 95% CI=0.49-0.87). Analysis by calendar year showed an increasing effectiveness from a 28% reduction in breast cancer mortality in the period 1975-1991 (OR=0.72; 95% CI=0.47-1.09) to 65% in the period 1992-2008 (OR=0.35; 95% CI=0.19-0.64).

CONCLUSION

Our results show an increasingly strong reduction in breast cancer mortality over time because of mammographic screening.

Population-based mammography screening below age 50: balancing radiation-induced vs prevented breast cancer deaths

INTRODUCTION

Exposure to ionizing radiation at mammography screening may cause breast cancer. Because the radiation risk increases with lower exposure age, advancing the lower age limit may affect the balance between screening benefits and risks. The present study explores the benefit-risk ratio of screening before age 50.

METHODS

The benefits of biennial mammography screening, starting at various ages between 40 and 50, and continuing up to age 74 were examined using micro-simulation. In contrast with previous studies that commonly used excess relative risk models, we assessed the radiation risks using the latest BEIR-VII excess absolute rate exposure-risk model.

RESULTS

The estimated radiation risk is lower than previously assessed. At a mean glandular dose of 1.3 mGy per view that was recently measured in the Netherlands, biennial mammography screening between age 50 and 74 was predicted to induce 1.6 breast cancer deaths per 100,000 women aged 0-100 (range 1.3-6.3 extra deaths at a glandular dose of 1-5 mGy per view), against 1121 avoided deaths in this population. Advancing the lower age limit for screening to include women aged 40-74 was predicted to induce 3.7 breast cancer deaths per 100,000 women aged 0-100 (range 2.9-14.4) at biennial screening, but would also prevent 1302 deaths.

CONCLUSION

The benefits of mammography screening between age 40 and 74 were predicted to outweigh the radiation risks.

How to enhance physician and public acceptance and utilisation of colon cancer screening recommendations

Colorectal Cancer (CRC) screening delivery is a multidisciplinary undertaking, aiming at reducing mortality from and incidence of CRC without adversely affecting the health status of participants. The adoption of a public health perspective involves commitment to ensure equity of access and sustainability of the program over time. We reviewed available evidence concerning predictors of CRC screening uptake and the impact of interventions to improve adoption of screening using conceptual frameworks defining the role of determinants of preventive behaviours and the reach and target of interventions. The results of this review indicate that policy measures aimed at supporting screening delivery, as well as organisational changes, influencing the operational features of preventive services, need to be implemented, in order to allow individual's motivation to be eventually realised. To ensure coverage and equity of access and to maximise the impact of the intervention, policies aimed at implementing organised programs should be adopted, ensuring that participation in screening and any follow-up assessment should not be limited by financial barriers. Participants and providers beliefs may determine the response to different screening modalities. To achieve the desired health impact, an active follow-up of people with screening abnormalities should be implemented, supported by the introduction of infrastructural changes and multidisciplinary team work, which can ensure sustainability over time of effective interventions. Continuous monitoring as well as the adoption of plans to evaluate for program effectiveness represent crucial steps in the implementation of a successful program.

A remarkable reduction of breast cancer deaths in screened versus unscreened women: a case-referent study

OBJECTIVE

We designed a case-referent study to investigate the effect of mammographic screening at the individual level, looking at the association of breast cancer death with screening history.

METHODS

The study population included all women aged 50-75 in the province of Limburg, the Netherlands who had been invited to the screening program from 1989 to 2006. From this population, 118 cases originated who died of breast cancer in 2004 or 2005. The screening history of these cases was collected and compared with a sample of the invited population. The breast cancer death rate in the screened relative to the unscreened women was estimated as the odds ratio (OR). This OR was adjusted for self-selection bias, the difference in baseline risk for breast cancer death between screened and unscreened women.

RESULTS

Analysis of the data showed a breast cancer mortality reduction of 70% in the screened versus the unscreened women (OR = 0.30, 95% CI 0.14-0.63). The magnitude of self-selection was estimated specifically for Limburg. After correction for self-selection bias, the effect of screening increased to 76% (OR = 0.24, 95% CI 0.10-0.58).

CONCLUSION

Screening resulted in a remarkable reduction in breast cancer mortality. Contrary to findings in other countries, adjustment for self-selection in Limburg had no influence on the impact of screening. Thanks to a well-organized centralized screening program, similar results are expected in other regions of the Netherlands.

Evaluation of cancer service screening: case referent studies recommended

Various cancer screening trials, randomised or otherwise controlled, have demonstrated reductions in cancer mortality. As a consequence, population screening programmes have been implemented. In the mean time, major advances are being made in early detection and treatment modalities of specific cancers and pre-cancers. The impact of these improvements should have bearing on the beneficial effect of periodical screening in preventing cancer death. To monitor these dynamics in the effectiveness of screening, case-referent studies are designed. The effectiveness is estimated by calculating an odds ratio indicating the cancer death rate in screened versus not screened invitees. The major criticisms of case referent studies are potential selection bias and confounding bias of the odds ratio. By properly designing and applying sensitivity analyses these biases can be minimised.

The other side of technology: risk of overdiagnosis of breast cancer with mammography screening

Estimates of overdiagnosis of breast cancer with mammography screening differ between studies. The estimate of overdiagnosis obtained using the cumulative incidence approach with data from randomized clinical trials ranges from 10 to 14%. In observational studies, where statistical adjustment for lead-time was utilized, the estimate was lower than 5% in two Italian studies, while it was quite higher in a Swedish study. Most of the differences are explained by different methodology, study design and measures. In this review we discuss the concept and the definition of the measure of overdiagnosis, and present different study methods to estimate overdiagnosis of breast cancer with mammography screening.