Volume 223 - Issue 11
The impact of the Breast Screen NSW transition from film to digital mammography, 2002–2016: a linked population health data analysis
Authors: Rachel Farber, Nehmat Houssami and Katy J L Bell
Med J Aust 2025; 223 (11): 679-679. || doi: 10.5694/mja2.70107
Published online: 8 December 2025
Published online: 8 December 2025
Reply
In reply: We thank Roder1 for the comment on our article. As reported in our article, interval cancer rates in New South Wales increased by 0.27 per 1000 screens after the shift to digital mammography.2 We agree the reason for the increase in the interval cancer rate remains unclear and warrants further investigation to understand the underlying factors. Possibilities include: (1) a real increase due to decreased detection of progressive cancers at the time of the change in technology; (2) a real increase due to increasing risk factors; or (3) an apparent increase due to increased detection external to BreastScreen. The interrupted time series analysis found that the transition was associated with an initial decrease in screen‐detected invasive cancers and an increase in interval cancers, suggesting that at least some of the additional interval cancers are attributable to the transition to digital mammography missing cancers (ie, false negatives), consistent with possibility number 1 of a decrease in detection of progressive cancers at the time of the change in technology. Subsequently, there was a year‐on‐year increase in the screen‐detected cancer rate accompanied by decreases in the interval cancer rate, suggesting increasing effectiveness in detecting clinically important cancer.
There is also evidence consistent with possibility number 3, with at least some of the apparent increase due to increased detection from new technologies such as tomosynthesis which are used outside of BreastScreen.3 The increase in interval cancers was attributed in part to ductal carcinomas in situ (DCIS) which rarely presents as symptomatic disease (invasive cancer and DCIS increased by 0.18 and 0.09 per 1000 screens respectively). Further, the invasive interval cancers diagnosed after the transition to digital mammography showed increases in early‐stage and smaller cancers (T1c 11–20mm) but decreases in late‐stage and larger cancers, compared with those diagnosed following film mammography.4 About 10% of women aged 40–74 years report attending a private screening outside of BreastScreen.5 However, how many attend both types of screening (and so could contribute to apparent interval cancer rates) is unknown.
Possibility number 2 is unlikely to explain most of the increase in interval cancers at the specific time point of the transition in mammography technology. Nevertheless, increasing rates of advanced stage cancer in the population suggest that there may be some real increase in the underlying risk for clinically significant disease.6
Competing interests
No relevant disclosures.
Authors’ contributions:
Rachel Farber: Writing – original draft. Nehmat Houssami: Writing – review and editing. Katy Bell: Writing – review and editing.
Acknowledgements
This work was supported by funding from the Australian National Health and Medical Research Council (NHMRC) Centre for Research Excellence (CIA Barratt, 1104136). Rachel Farber declares funding from NHMRC (1168688) and National Breast Cancer Foundation (NBCF) (DS‐19‐02). Katy Bell is the recipient of an NHMRC Investigator Grant (#1174523). Nehmat Houssami is a recipient of a NHMRC Investigator grant (#1194410) and an NBCF Chair in Breast Cancer Prevention grant (#EC‐21‐001). The funders of the study had no role in study design or data collection.
References
- Roder DM. The impact of the BreastScreen NSW transition from film to digital mammography, 2002–2016: a linked population health data analysis [letter]. Med J Aust 2025; 223: 678.
- Farber R, Houssami N, McGeechan K, et al. The impact of the BreastScreen NSW transition from film to digital mammography, 2002–2016: a linked population health data analysis. Med J Aust 2025; 222: 82‐90. https://www.mja.com.au/journal/2025/222/2/impact‐breastscreen‐nsw‐transition‐film‐digital‐mammography‐2002‐2016‐linked
- Noguchi N, Boroumand F, Bell K, et al. Diagnostic performance of digital breast tomosynthesis (DBT) versus digital mammography (DM) in a population clinically referred for breast imaging — a retrospective cohort study. Cancer Treat Res Commun 2024; 42: 100865.
- Farber R, Houssami N, McGeechan K, et al. Breast cancer stage and size detected with film versus digital mammography in New South Wales, Australia: a population‐based study using routinely collected data. Cancer Epidemiol Biomarkers Prev 2024; 33: 671‐680.
- Li T, Marinovich ML, Ormiston‐Smith N, et al. Factors associated with private or public breast cancer screening attendance in Queensland, Australia: a retrospective cross‐sectional study. J Med Screen 2024; 31: 258‐262.
- Jacklyn G, McGeechan K, Irwig L, et al. Trends in stage‐specific breast cancer incidence in New South Wales, Australia: insights into the effects of 25 years of screening mammography. Breast Cancer Res Treat 2017; 166: 843‐854.