Why mammography screening has not lived up to expectations from the randomised trials.

We analysed the relation between tumour sizes and stages and the reported effects on breast cancer mortality with and without screening in trials and observational studies. The average tumour sizes in all the trials suggest only a 12% reduction in breast cancer mortality, which agrees with the 10% reported in the most reliable trials. Recent studies of tumour sizes and tumour stages show that screening has not lowered the rate of advanced cancers. In agreement with this, recent observational studies of breast cancer mortality have failed to find an effect of screening. In contrast, screening leads to serious harms in healthy women through overdiagnosis with subsequent overtreatment and false-positive mammograms. We suggest that the rationale for breast screening be urgently reassessed by policy-makers. The observed decline in breast cancer mortality in many countries seems to be caused by improved adjuvant therapy and breast cancer awareness, not screening. We also believe it is more important to reduce the incidence of cancer than to detect it 'early.' Avoiding getting screening mammograms reduces the risk of becoming a breast cancer patient by one-third.