Interval breast cancers in an Australian mammographic screening program.
OBJECTIVE
To determine the incidence of interval cancers which occurred in the first 12 months after mammographic screening at a mammographic screening service.


METHODS
Retrospective analysis of data obtained by crossmatching the screening Service and the New South Wales Central Cancer Registry databases.


METHODS
The Central & Eastern Sydney Service of BreastScreen NSW.


METHODS
Women aged 40-69 years at first screen, who attended for their first or second screen between 1 March 1988 and 31 December 1992.


METHODS
Interval-cancer rates per 10000 screens and as a proportion of the underlying incidence of breast cancer (as estimated by the underlying rate in the total NSW population).


RESULTS
The 12-month interval-cancer incidence per 10000 screens was 4.17 for the 40-49 years age group (95% confidence interval [CI], 1.35-9.73) and 4.64 for the 50-69 years age group (95% CI, 2.47-7.94). Proportional incidence rates were 30.1% for the 40-49 years age group (95% CI, 9.8-70.3) and 22% for the 50-69 years age group (95% CI, 11.7-37.7). There was no significant difference between the proportional incidence rate for the 50-69 years age group for the Central & Eastern Sydney Service and those of major successful overseas screening trials.


CONCLUSIONS
Screening quality was acceptable and should result in a significant mortality reduction in the screened population. Given the small number of cancers involved, comparison of interval-cancer statistics of mammographic screening programs with trials requires age-specific or age-adjusted data, and consideration of confidence intervals of both program and trial data.
Rickard
M T
MT
Department of Public Health and Community Medicine, Faculty of Medicine, University of Sydney, NSW. Mary@ces.bci.org.au
Taylor
R J
RJ
Fazli
M A
MA
El Hassan
N
N
D000328:Adult; D000368:Aged; D019985:Benchmarking; D001943:Breast Neoplasms / Q000401:mortality*; D002568:Certification; D003431:Cross-Cultural Comparison; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008327:Mammography / Q000706:statistics & numerical data*; D008403:Mass Screening / Q000706:statistics & numerical data*; D008875:Middle Aged; D009517:New South Wales; D010043:Outcome and Process Assessment, Health Care / Q000706:statistics & numerical data*; D011785:Quality Assurance, Health Care / Q000706:statistics & numerical data*; D016019:Survival Analysis