Are international differences in breast cancer survival between Australia and the UK present amongst both screen‐detected women and non‐screen‐detected women? survival estimates for women diagnosed in West Midlands and New South Wales 1997–2006

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.

Impact of deprivation on breast cancer survival among women eligible for mammographic screening in the West Midlands (UK) and New South Wales (Australia): Women diagnosed 1997–2006

“…Because mammography is obtained in Australia both through BreastScreen and the Medicare Benefits Scheme (MBS), de facto screening is likely to occur to a certain degree, which means that some women in New South Wales recorded in our study as never attenders, were, in fact, screen‐detected. We have shown, however, by a sensitivity analysis in which the proportion of women in the screen‐detected group was modified, that the differences observed are robust to this bias . Although it is probable that we incorrectly allocated some women to the never‐attender group in New South Wales, information on their personal characteristics and the features of their cancer would not have been compromised since these data items were collected from the Cancer Registry, rather than via the screening service.…”

“…These biases together lead to apparently better survival in the screen‐detected group when not appropriately considered. We discuss the interpretation of these corrected rates in detail in the companion paper …”

“…The data have been described . Briefly, the cohort consisted of women diagnosed with an invasive, primary breast cancer at age 50–65 years during the period January 1, 1997 to December 31, 2006 and aged 51 years or younger on 1 January 1997.…”

“…Our methods have been described in detail . Briefly, we estimated net survival using the non‐parametric Pohar‐Perme estimator .…”

“…Screening thus provides an opportunity to examine the contributions of the timeliness of diagnosis and stage of disease to socioeconomic differences in survival. In a companion article, we have examined international differences in survival between screened and non‐screened women from West Midlands and New South Wales who had been eligible for screening from their 50th birthday . We found that net survival was persistently higher in New South Wales than in the West Midlands, among both screen‐detected and non‐screen‐detected women.…”