The Canadian national breast screening study. Why? what next? and so what?

Why the National Breast Screening Study (NBSS)? In 1979, after reviewing the Breast Cancer Detection Demonstration Projects (BCDDP), the Beahrs Working Group made 11 recommendations. The NBSS protocol reflected a number these recommendations, particularly the evaluation screening women age 40–49 and the still unanswered question the incremental benefit mammography versus physical examination the breasts among women age 50–59. Three years after publication NBSS's 7‐year results and in light other published evidence from screening trials (as opposed to observational studies), it is reasonable to recommend screening with mammography and physical examination every 2 years for women age 50–59. In contrast, it is not reasonable to offer screening mammography to women age 40–49 other than in the context a controlled trial, an opportunity currently available in the United Kingdom. The Beahrs recommendation, that “physical examinations should be continued in the Breast Cancer Detection Demonstration Projects as a routine screening modality for all ages,” remains justifiable as long as so many women age 40–49 are having mammograms performed, given the relatively poor sensitivity mammography in this age group. Criticism the NBSS, mainly by radiologists, will continue until the NBSS yields results that support its critics' belief in the efficacy screening. To date, responses to critics of the NBSS have focused on correcting misinformation and clarifying NBSS procedures. Useful critical commentary should await the results a 10‐year NBSS follow‐up and the U.S. National Cancer Institute‐sponsored meta‐analysis screening trials. Rigorous critical scrutiny should be directed at all trials. Cancer 1995; 76:2107–12.