Monitoring interval cancers in an Australian mammographic screening programme.
OBJECTIVE
To report the interval cancer rate for BreastScreen Victoria.


METHODS
Electronic linkage of Breast Screen Victoria records with those of the Victorian Cancer Registry. Interval cancers were expressed as a proportion of the underlying incidence (proportional incidence), and the sensitivity as the number of screen detected invasive breast cancers divided by the total number of invasive breast cancers diagnosed in the screening interval.


METHODS
Victoria, Australia where biennial screening is provided to women aged 40 and older.


METHODS
Victorian women aged 40-79 who attended first round screening in 1994 (103,023 women) and 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 screening was 59% in 40-49 year old women and 27% in women aged 50-69. In the second year the proportional incidence was 93% in 40-49 year old women and 54% in women aged 50-69.


CONCLUSIONS
Interval cancers comprise such a large proportion of the expected 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 found in this study was similar to those found in the UK programmes.
Kavanagh
A M
AM
Cancer Epidemiology Centre, Anti-Cancer Council Victoria, Carlton South, Australia.
Mitchell
H
H
Farrugia
H
H
Giles
G G
GG
D000328:Adult; D017677:Age Distribution; D000368:Aged; D001315:Australia / Q000453:epidemiology; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000453:epidemiology*; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D015994:Incidence; D008327:Mammography / Q000379:methods*; D008403:Mass Screening / Q000706:statistics & numerical data*; D008875:Middle Aged; D012680:Sensitivity and Specificity; D013997:Time Factors