Project 3: Breast screening evidence

Project 3: Breast screening evidence

Work by Gemma Jacklyn, supervised by Alex Barratt

One of the difficulties in making good judgements about cancer screening is that often the benefits of screening are far more extensively studied than the harms. This means that it is difficult to determine whether and how the benefits may outweigh the harms of screening

Gemma is working to produce a new statistical model that will provide the best estimate to date of the extent of the harm of overdiagnosis in Australian breast screening. She is updating and extending an existing Markov process model with data from BreastScreen Australia, the Australian institute of Health and Welfare, and the Australian Bureau of Statistics to produce age specific outcomes of breast cancer screening expressed per 1000 women over 20 (and 30) years. Updated outcomes will include breast cancer deaths prevented, false positives (recalls for more imaging and biopsies) and interval cancers. The model will be extended to include overdiagnosed cancers, and if possible, breast cancers caused by radiation from mammography and late deaths due to breast cancer treatments (e.g. extra deaths from myocardial infarction and lung cancer after radiotherapy). Gemma will obtain estimates of overdiagnosis due to mammography screening in Australia using several approaches. The results will be adjusted for the methodological issues and biases that distort estimates of overdiagnosis – including pre-screening incidence, participation rates and lead time – and then compared. This will complement existing knowledge about benefits, to produce more complete knowledge about the effects of cancer screening to inform practice and policy.

Publications arising to date from this study are provided below:

Jacklyn G, Glasziou P, Macaskill P, Barratt A. Meta-analysis of breast cancer mortality benefit and over diagnosis adjusted for adherence: improving information on the effects of attending screening mammography. British Journal of Cancer. 2016; Apr 28. doi: 10.1038/bjc.2016.90. [Epub ahead of print]

Barratt A, Jacklyn GL. Challenges in Understanding and Quantifying Overdiagnosis and Overtreatment. In: Houssami N, Miglioretti D, editors. Breast Cancer Screening: An Examination of Scientific Evidence. London, UK: Elsevier; 2016.