Since 1985, 5411 patients were randomized in four large randomized clinical trials assessing the role of adjuvant radiotherapy and/or tamoxifen in breast conserving surgery for patients with ductal carcinoma in situ (DCIS).

First the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-17 trial proved relevance of postoperative radiotherapy in breast conserving surgery in DCIS patients: an approximately 50% reduction of ipsilateral tumour recurrences. This is confirmed by longer time of follow-up and validated by data from the European Organization for Research and Treatment of Cancer (EORTC) 10853 and UK Coordinating Committee on Cancer Research (UKCCCR) DCIS trials. A subset of patients who do not benefit of adjuvant radiotherapy cannot be identified. Completeness of excision proved to be the most important treatment variable to reduce local recurrence.

Both the NSABP B-24 and UKCCCR DCIS trials investigated the effect of tamoxifen resulting in contradictory findings. In addition a possible benefit seems to be restricted to oestrogen receptor-positive DCIS lesions nourishing the existent reserve in prescribing tamoxifen for all patients with DCIS.

The failure to materialize a difference in survival by the effect of either adjuvant radiotherapy or tamoxifen endorses the favourable outcome of DCIS. Currently, four other randomized clinical trials investigate the role of radiotherapy, tamoxifen, anastrazole, or no further treatment for a selected group of patients.

Mammographic density is a well-documented independent risk factor for breast cancer. Measurements of density come in various forms, ranging from qualitative descriptions to quantitative assessments or a combination of both. The different means of examining density lead to variations in density–risk relationship. Currently there is no consensus on which method is preferable. The interrelation of mammographic density with other risk factors is crucial to density–risk assessments, since each of these risk factors can influence density on its own. Mammographic density can be modified through hormonal and chemical means, which can have important implications on mammographic sensitivity, accuracy in cancer diagnosis and cancer prevention.

Five to ten per cent of all breast cancers are associated with a proven genetic predisposition for the disease or a strong family history of breast cancer in which yet unknown genetic predisposition is suspected. Carriers of germline mutations in genes breast cancer 1 or 2 (BRCA1/2) have up to 85% chance of developing breast cancer during their lifetime. The majority of these women develop the disease before the age of 50 years. Consequently, breast-cancer screening programmes aimed at reducing mortality in this population may only be effective if they start at much younger age than the general breast-cancer screening programmes. Unfortunately, the efficacy of conventional X-ray mammography in premenopausal women is often limited by dense fibroglandular tissue that obscures suspicious lesions. As a result, more advanced breast-imaging techniques have been considered, such as contrast-enhanced (CE) magnetic resonance imaging (MRI). In symptomatic patients, the sensitivity of CE MRI to detect invasive breast cancer is known to be high, regardless of the density of the fibroglandular tissue. Conversely, the specificity of CE MRI to discriminate between benign and malignant lesions is variable, and depends on the indication of the examination. Low specificity could result in many recalls on benign lesions, thus negatively affecting the cost–benefit ratio of CE MRI as a screening technique. Several single- and multi-institutional studies have been performed to investigate the efficacy of CE MRI as a screening tool exclusively for asymptomatic women at increased lifetime risk of breast cancer. Mounting evidence suggests that the addition of CE MRI results in cost-effective detection of tumours at earlier stage in BRCA1/2 mutation carriers. The value of CE MRI in other populations at risk is currently uncertain, and it is unlikely that CE MRI will be cost efficient in the general screening population of women who are not at increased lifetime risk.