Estimating the cost-effectiveness of risk stratified breast cancer screening in the UK

Background

In the United Kingdom, the National Health Service Breast Cancer Screening Programme (NBCSP) invites women aged 50–70 years to attend for 3-yearly mammograms. Most other countries invite women to biennial screening. Disparities across countries exist in the status of implementation due to considerable debate around the harms and benefit of breast screening. One approach that may improve the harm-to-benefit balance is to risk-stratify breast cancer screening. There has been growing interest in the UK and internationally of risk stratified breast screening whereby individualised risk assessment may inform screening frequency, starting age, screening instrument used, or even decisions not to screen. This study evaluates the cost-effectiveness of eight proposals for risk-stratified screening regimens, developed by independent research groups (ASSURE, PROCAS and BRAID), compared to the current UK screening programme and compared to no national screening.

Methods

A de novo discrete-event simulation model was developed to simulate population-level screening in women who are followed over their lifetime. Health related quality of life, cancer survival, and treatment costs are estimated conditional on cancer stage (non-invasive cancer and four invasive cancer stages), age at cancer detection and duration of time since the cancer was detected. Tumour detection at screening was modelled to be dependent on breast density and tumour size.

The main mechanism of generating a benefit of screening in the model is a stage-shift; screen detected cancers are assigned an earlier stage and have improved survival. Harms of screening are overdiagnosis (women who receive treatment for cancers that would have never presented symptomatically without screening), pain incurred during mammography screening, and false positive results, all of which incur a QALY loss. Model outcomes were validated against audit data from the NBCSP.

Results

Compared with the current screening programme, all risk-stratified regimens generated additional costs and QALYs, and had a larger net monetary benefit. No screening amongst the lowest risk group, and triannual, biennial and annual screening amongst the three higher risk groups was the optimal screening strategy.