[Effects of the population screening into breast cancer]. / Effecten van het bevolkingsonderzoek naar borstkanker.

Annually, in the Netherlands around 900,000 women between the ages of 50-75 years undergo mammography as part of a population screening into breast cancer. In this way more than 5000 cases of breast cancer are detected (0.6% of women screened); 70% of these malignancies are < stage II, which is prognostically favourable. Due to the early detection and treatment of breast cancer, the breast cancer death risk in those women who participate in the population screening is half that of women who choose not to be screened. The downside of the population screening is that participants are relatively often referred to a hospital for a diagnostic work-up (around 2%), and 70% of them are ultimately found not to have cancer. The positive predictive value of the population screening is 30%. Early discovery also leads to over-diagnosis in patients with breast cancer that without screening would never have manifested itself. Based on computer simulations it has been estimated that in the Netherlands over-diagnosis occurs in 9% of patients in whom breast cancer is detected during a population screening.

[Computerised assessment of screening mammograms]. / Computerbeoordeling van screeningsmammogrammen.

More than one million mammograms are performed in the Netherlands each year. Today, these images are all in digital format and processed by various types of software for optimal display during radiological analysis. As a result of continuous quality control on national public health screening for breast cancer, approximately 1000 cases of interval carcinoma and any T2 tumours identified during this screening are re-assessed. The results of these retrospective analyses suggest that there is room for improvement in terms of the reliability of screening mammography without this resulting in an excessive increase of false positive results. Research has shown that the more radiological evaluators are involved, the better the results. Alternatively, a computer can be utilised for detecting abnormalities. Large-scale use of Computer-Assisted Detection (CAD) is already underway in some countries. For this reason, the option of adding CAD to the current practice of double assessment of mammograms could be considered a sensible option for the future.