There has been much debate in recent years about the relative benefits and risks of screening. Debates about breast cancer screening have been particularly heated, even though such screening is recommended in most developed countries. Concerns raised in a recent major review of the benefits and risks of the UK breast screening programmes are also at the heart of discussions about prostate specific antigen testing, where there is evidence of benefit but also of considerable risks.1 2 In a linked research paper (doi:10.1136/bmj.e8441), Lee and colleagues consider how long it might take for the benefits of screening to show in a population invited for breast or bowel cancer screening.3

Where benefits are considered to outweigh risks then screening can be recommended. In developed countries and jurisdictions where a population model of health is delivered, screening for breast, cervical, and bowel cancer is often offered on an organised basis.4 5 Evaluation of the effectiveness of such programmes is demanded …