Sir: The headline "Tests missed breast cancer" that accompanied an otherwise mature piece on breast screening (17 January) is inaccurate and can lead to women wrongly believing that there is little value in being screened. We make it clear in our paper, published in the British Medical Journal, that the problem of cancers occurring in women in the screening interval is largely due to these cancers growing as new cancers after a previous screen. After careful comparison of screening X-rays and X-rays taken at the time of diagnosis, a small number of interval cancers will be considered in hindsight by radiologists to have been detectable at the time of the previous screening.
To put this problem in perspective, out of every 10,000 women screened, approximately 60 cancers will be detected earlier at screening and eight will be "missed" because subtle radiological features were overlooked.
Yours sincerely, C.B.J. Woodman Director A. G. Threlfall Centre for Cancer Epidemiology University of Manchester Manchester