Monitoring interval cancers in an Australian mammographic screening programme

Objective-To report the interval cancer rate for BreastScreen Victoria. Design-Electronic :linkage of Breast Screen Victoria records with those of the Victorian Cancer Registry. Interval cancers were expressed as a proport ion of the underlying incidence (proportional incidence), and the sensitivi ty as the number of screen detected invasive breast cancers divided by the total number of invasive breast cancers diagnosed in the screening interval . Setting-Victoria, Australia where biennial screening is provided to women a ged 40 and older. Subjects-Victorian women aged 40-79 who attended first round screening in 1 994 (103 023 women) sind 1995 (107 057 women). Results-The sensitivity of screening mammography for the two year interval increased with age (p for trend < 0.001) and was 49.4% in women aged 40-49, 68.6% in 50-59 year old women, 80.7% in 60-69 year old women, and 85.2% in women aged 70-79. The proportional incidence in the first year after scree ning was 59% in 40-49 year old women and 27% in women aged 50-69. In the se cond year the: proportional incidence was 93% in 40-49 year old women and 5 4% in women aged 50-69. Conclusions-Interval cancers comprise: such a large proportion of the expec ted number of cancers in 40-49 year old women that the benefit of screening is likely to be low. For women aged 50-69, the proportional incidence foun d in this study was similar to those found in the UK programmes.