B35
Randomised controlled trial of mammographic screening in young women: updated results on incidence and mortality
Sue Moss1, Louise Johns1, Howard Cuckle2, Lynda Bobrow5, Andy Evans6, Liz Kutt3, Carol Record4
1Institute of Cancer Research, Sutton, UK, 2University of Leeds, UK, 3Addenbrookes NHS Trust, Cambridge, UK, 4Nottingham University Hospitals NHS Trust, Nottingham, UK, 5Bristol Royal Infirmary, Bristol, UK, 6Stoke Mandeville Hospital, Aylesbury, UK
The Age trial was a randomised controlled trial designed to study the effect of inviting women for mammography from age 40 compared with the then current NHS policy under which women are invited for 3 yearly screening from age 50. In total, 160,921 women were randomised in the ratio 1:2 to an intervention arm offered annual mammography to age 48 and a control arm which received usual medical care. We have previously reported a non-significant 17% decrease in breast cancer mortality in the intervention arm at a mean follow-up of 10.7 years.
Updated results at a mean follow-up of 13.6 years give a rate ratio of breast cancer death in the intervention arm of 0.86 (95% ci 0.71-1.04), equivalent to an absolute reduction of 0.46 per 1000 women invited for screening, or a number needed to screen of 2167. The mortality reduction in compliers, adjusted for the rate in non-compliers, was 19%. Restricting deaths from breast cancer to those diagnosed within 10 years of randomisation had little impact on the results. Approximately 85 % of trial women have now been invited for screening at ages 50-52; cumulative incidence of breast cancer in these women is similar in the two trial arms, but there is a higher proportion of in situ cancers in the intervention arm. Uptake of screening at ages 50-52 appears slightly reduced in the intervention arm.
The relative risk of breast cancer death in the intervention arm has not decreased with longer follow up, although the absolute reduction has increased. Screening in this age group appears to result in little if any over-diagnosis.
