Abstract
We examined survival in screened‐detected and non‐screen‐detected women diagnosed in the West Midlands (UK) and New South Wales (Australia) in order to evaluate whether international differences in survival are related to early diagnosis, or to other factors relating to the healthcare women receive. Data for women aged 50 − 65 years who had been eligible for screening from 50 years were examined. Data for 5,628 women in West Midlands and 6,396 women in New South Wales were linked to screening service records (mean age at diagnosis 53.7 years). We estimated net survival and modelled the excess hazard ratio of breast cancer death by screening status. Survival was lower for women in the West Midlands than in New South Wales (5‐year net survival 90.9% [95% CI 89.9%−91.7%] compared with 93.4% [95% CI 92.6%‐94.1%], respectively). The difference was greater between the two populations of non‐screen‐detected women (4.9%) compared to between screen‐detected women, (1.8% after adjustment for lead‐time and over‐diagnosis). The adjusted excess hazard ratio of breast cancer death for West Midlands compared with New South Wales was greater in the non‐screen‐detected group (EHR 2.00, 95% CI 1.70 − 2.31) but not significantly different to that for women whose cancer had been screen‐detected (EHR 1.72, 95% CI 0.87 − 2.56). In this study more than one in three breast cancer deaths in the West Midlands would have been avoided if survival had been the same as in New South Wales. The possibility that women in the UK receive poorer treatment is an important potential explanation which should be examined with care.
Highlights
We have previously shown a difference of 6 per cent in five-year breast cancer survival between Australia and England for women in the target age group for screening and diagnosed during the period 1996-1999.1 Examining survival by screening status has the potential to further shed light on whether international differences are more likely to be due to tumour or patient factors or to other factors relating to the healthcare women receive
We examine net survival for breast cancer in screen-detected and non-screen-detected women diagnosed in the West Midlands (England) and New South Wales (Australia), applying a correction for lead-time bias and over-diagnosis
We analysed data for 5,628 women in West Midlands (98.5% of those eligible, mean age at diagnosis 53.7 years) and 6,396 women in New South Wales (99.9% of those eligible, mean age at diagnosis 53.8 years). Those excluded were the very small number of women who were known to the registry only because breast cancer had been mentioned on their death certificate (DCOs) or because the sequence of dates provided was illogical
Summary
We have previously shown a difference of 6 per cent in five-year breast cancer survival between Australia and England for women in the target age group for screening and diagnosed during the period 1996-1999.1 Examining survival by screening status has the potential to further shed light on whether international differences are more likely to be due to tumour or patient factors or to other factors relating to the healthcare women receive. The trials that led to the implementation of mammographic screening worldwide were evaluated by examining the reduction in breast cancer mortality amongst the populations of women screened.[3] In this context, a reduction in the number of breast cancer deaths in the screened population can be interpreted as the number of cancer deaths avoided or deferred by the intervention. This outcome is helpful in evaluating the public health impact and economic value of the screening programme as a whole. The review identified the importance of linkage of mortality data to screening invitations so that the outcome for tumours diagnosed after the introduction of screening might be examined
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