Breast cancer screening with mammography: a population-based, randomized trial with mammography as the only screening mode.

A population-based, randomized breast cancer screening project was undertaken using mammography alone. Of 17,447 invited women aged 50-69, 12,765 (73%) attended the screening. On the basis of the screening films, malignancy was suspected in 405 women (3.2%) who were recalled for complete mammography. Additional films showed that the suspicion of malignancy was false in 194 women. The remaining 211 women (1.7%) were referred for clinical and cytological examination. Of these, 159 had surgery. Breast cancer was proved in 97 women, corresponding to a prevalence rate of 7.6/1000. Fifty-three (55%) of the carcinomas were either in situ or invasive with a diameter of less than or equal to 1 cm. Axillary metastases were found in 19 patients (19.6%). Cancers detected at screening were significantly less advanced than those in the control group. There was a remarkably high frequency of tubular carcinoma among cancers detected at screening.