The National Breast Cancer Audit (NBCA) of the Royal Australasian College of Surgeons has been collecting information from surgeons on the treatment of their patients who were diagnosed with breast cancer since 1998. This data is used to assess surgeon performance, as well as for research into early breast cancer treatment in Australia and New Zealand.

As the data does not include information on how many patients survive, researchers decided to link the audit database to the central database of deaths at the Australian Institute of Health and Welfare, the National Death Index (NDI). However, the NBCA data only uses the first three letters of the patient's name and the date of birth, to protect privacy. Researchers wanted to make sure that linked NDI data would refer to the same patient and not another person with a similar name.

A pilot study was conducted in South Australia (SA), in which data on a small number of patients recorded in the NBCA and also the SA Cancer Registry were linked to the SA death records. The two linkages gave similar results.

The remaining Australian cases in the NBCA database were then linked with the NDI data, and the results were compared with reported survival rates of patients with breast cancer in New South Wales and the United States of America. The survival rates were similar in all three databases.

This study showed that the data of the NBCA and the NDI can be linked successfully. The NBCA data can now be used to consider how factors like age, screening and differences in treatment affect the survival of Australian breast cancer patients.