Hard lessons from a randomised controlled trial.

detected invasive cancer will have a better prognosis and live longer, provided lead-time bias does not negate the prognostic effect of lower staging by detecting cancer earlier while not influencing the natural history of the disease. The prognostic significance of non-invasive cancer (ductal carcinoma in situ), its treatment and the appropriateness of various local and systemic treatments for any breast cancer can be debated and argued. However, the histopathological prognostic (TNM) data would suggest that mammographic screening by high-quality programs successfully detects cancers at an earlier stage, giving a better prognosis and probably improved survival. Women should be made aware of these facts, along with any doubts raised by reviewers of somewhat out-of-date trials.