Breast screening histories: variation with time and impact on 10-year survival

Every case of primary breast cancer diagnosed in the West Midlands since screening began until 31 March 2001 was assigned a screening status based on the woman's screening history. Eligible cases were identified from the West Midlands Cancer Intelligence Unit's cancer registration database. Screen-detected (SD) tumours were identified through regional breast screening units. The remaining tumours were allocated to one of eight screening status categories.

A total 14,625 breast cancers were classified. The number of SD, interval cancers (IC), and cancers in lapsed attenders increased over time. There was a decrease over time in the number of cancers diagnosed in women before invitation and in nonattenders. IC rates were lower 24–36 months from screening to diagnosis compared with 12–24 months. Around one-third of cancers in lapsed attenders and nonattenders were diagnosed within 8 months of their last invitation, suggesting that they may have been screening provoked.

There was a significant difference in the 10-year relative survival rates for attenders (SD, IC, lapsed attenders and nonattenders; 85.2% and 53.9%, respectively; RR = 1.58; P < 0.00001). Women with IC had survival rates above those of nonattenders, highlighting the benefits of screening.

Table 1