Evaluation of the population dose to the UK population from the National Health Service breast screening programme

Abstract

In the United Kingdom National Health Service Breast Screening Programme (NHSBSP), women aged between 50 and 70 y are invited for mammography every 3 y. Screening histories for each woman, over four screening rounds, were analysed. Data from five screening programmes were used to select 57,425 women into the study. Cases were selected on the basis of being between the ages of 50 and 53 at the start of the NHSBSP (i.e. between 1989 and 1992). Assessment of the outcome for each screening round for each woman involved assigning a simple outcome code. Each of the possible pathways through the four screening rounds was analysed. This comprises of 500 possible pathways. This data enabled the following information to be determined: (i) The number of times a woman attended the screening programme. (ii) The number of women referred for assessment at each screening round. This information may be used to deduce the population dose to this group of women averaged over four screening rounds. Patient doses have been monitored since the programme's inception and are typically 4.5 mGy for two-view screening. It is possible to determine the mean glandular dose received by this cohort of women over four screening rounds by multiplying the number of examinations by the mean glandular dose for a typical woman. Allowance has to be made for the number of projections taken at each screening round. Once a woman has been screened, she may be invited back for further assessment if an abnormality is found on her mammogram. A stereotactic attachment is used to determine where to place the biopsy device. Although the dose received during a normal screening mammogram is well known, the dose for a stereotactic procedure and other assessment procedures is less well known, partly because only a small part of the breast is directly irradiated during stereotaxis. However, the woman may have multiple exposures during this stage. A prospective survey of doses was completed to deduce the mean glandular dose at the first assessment stage and during stereotaxis. Numbers of films, including magnification films taken at first-stage assessment were established in the North East of England and Scotland by means of a postal survey. Average total mean glandular dose was deduced using previous survey data for the screening programme and a multiplying factor to allow for magnification film dose. On average 1.6 full field and 0.15 collimated contact films are taken for each woman (with 2.25 and 0.75 mGy film(-1)), 1.0 full field and 0.9 collimated magnification views. The mean magnification film dose to the assessed breast was 5.0 and 1.7 mGy for a collimated magnification film. A survey of 134 women at screening centres in the North East of England was performed to deduce the mean glandular dose from digital stereotaxis which is almost universally used in breast screening. A typical woman received a dose to the assessed breast of 4.5 mGy with a range of 1.3-17 mGy. This data may be used to deduce the total mean glandular dose over four screening rounds includi...

Breast Cancer Risk from Different Mammography Screening Practices

“…Even though ICRP detriment-adjusted nominal risk coefficients are not meant for risk estimation, one could estimate that this would lead to 207 fatal breast tumors among the 900,000 women screened. Similarly, in the United Kingdom the collective glandular dose from mammography screening has recently been estimated at 8094 Gy per year (28). This amounts to 971 Sv per year using the new ICRP 103 tissue weighting factor.…”

Estimates of the potential risk of radiation-related cancer from screening in the UK

“…To conduct the calculations organ-specific radiation doses were estimated for each screening test from survey information 6 or screening protocols 7–9 and these were multiplied by the estimated lifetime risk of radiation-related cancer for each organ, for the relevant age at exposure and sex. 3 The total cancer risk was then calculated by summing across all the exposed organs.…”

“…The dose estimates for mammographic screening were based on national dose survey data from the UK. 6 For the other screening examinations the doses were estimated using published screening protocols. 7–9 These have been developed specifically to ensure low doses whilst maintaining the necessary image quality.…”