Impact of population screening programs on cancer outcomes

Age-standardised breast cancer mortality fell by around 26% in Australian females in the 15 years following introduction of the BreastScreen Australia program. The relative contributions of breast screening and treatment advances to this reduction are open to debate. Three evaluations of breast screening in Australia point to reductions in breast cancer mortality in screening participants consistent with the collective trial results, estimated to be around 35% by an expert panel of the International Agency for Research on Cancer. The collective results of evaluations in other countries are similar but individual results vary widely, from little or no benefit to reductions of up to 76%. Over-diagnosis is a controversial issue, with some results indicating it to be of negligible magnitude and others indicating that it could represent 30% or more of breast cancers in populations exposed to breast screening. Meanwhile, age-standardised cervical cancer mortality reduced by over 50% in the 15 years following introduction of an organised approach to screening. This followed earlier reductions also likely to reflect cervical screening. The roll-out of bowel screening in 2006 is too recent for reporting on effects on colorectal cancer mortality, although it is expected that effects from the one-off screening offered at 50, 55 and 65 years of age would be less than in trials where annual or biennial screening was undertaken.