Mary Rickard

Comparison of the validity and reliability of two image classification systems for the assessment of mammogram quality.

Objective: To compare the reliability and validity of two classification systems used to evaluate the quality of mammograms: PGMI (perfect, good, moderate and inadequate) and EAR (excellent, acceptable and repeat). Setting: New South Wales (Australia)population-based mammography screening programme (BreastScreen NSW). Methods: Thirty sets of mammograms were rated by 21 radiographers and an expert panel. PGMI and EAR criteria were used to assign ratings to the medio-lateral oblique (MLO) and cranio-caudal (CC) views for each setof films. Inter-observer reliability and criterion validity (compared with expert panel ratings) were assessed using mean weighted observed agreement and kappa statistics. Results: Reliability : Kappa values for both classification systems were low (0.01–0.17). PGMI producedsignificantly higher values than EAR. Agreement between raters was higher using PGMI than EAR for the MLO view (77% versus 74%, P<0.05), but was similar for the CC view. Dichotomized ratings (acceptable or needs repeating) did not improve reliability estimates. Validity : Kappavalues between raters and the reference standard were low for both classification systems (0.05–0.15). Agreement between raters and the reference standard was higher using PGMI than EAR for the MLO view (74% versus 63%), but was similar for the CC view. Dichotomized ratings of the MLOview showed slightly higher observer agreement. Conclusions: Both PGMI and EAR have poor reliability and validity in evaluating mammogram quality. EAR is not a suitable alternative to PGMI, which must be improved if it is to be useful.

Population-based mammography screening and breast cancer incidence in New South Wales, Australia

ObjectiveTo analyse breast cancer incidence trends in New South Wales (NSW), Australia, in relation to population-based mammography screening targeting women aged 50 to 69xa0years.MethodsTrends in age-specific incidence of invasive breast cancers in NSW women aged ≥40xa0years were examined in relation to mammography screening rates and screening cancer detection rates.ResultsIncidence of invasive breast cancer in NSW women increased in all age-groups over 1972 to 2002. The incidence trend for women aged 50 to 69xa0years showed that the steepest rise was associated with increased participation in population-based mammography screening, which was implemented from 1988 and achieved state-wide coverage in 1995. The elevated incidence of invasive cancer significantly exceeded pre-screening levels, and persisted after rates of initial screens declined. This elevated incidence was sustained by the contribution of cancers diagnosed through subsequent screening, and resulted from increased cancer detection rates in subsequent screens.ConclusionsThe recent increase in invasive breast cancer incidence in NSW is associated with mammography screening, and occurred mostly in the target age-group women. Persistence of higher incidence after 1994 was not explicable by inflation of cancer incidence due to detection of prevalent screen cases, but was associated with a trend of increased cancer detection rates in subsequent screening rounds, probably consequent to quality improvements in mammography screening diagnosis.

Age-specific interval breast cancers in New South Wales and meta-analysis of studies of women aged 40-49 years

Objective: To compare interval cancers in the 40–49 year age group with other age groups in New South Wales and with published trials and service studies. Setting: New South Wales data were derived from the population-based biennial mammography screening program, which achieved state-wide coverage in 1995. Women aged 40–49 years screened during 1995–1998 were included. Methods: Bilateral two-view mammography with reading by two radiologists was employed for biennial screening examinations. Interval cancers were detected by the screening program and by linkage with the state-wide cancer registry. Incidence of interval cancer based on the date of diagnosis was estimated as a proportion of the expected underlying breast cancer incidence for first- and second-year interval cancers. Sensitivity estimates were also calculated. Comparative data for the 40–49 year age group were derived from the published literature for meta-analyses of trial and service studies. Results: Interval cancer rates for New South Wales decreased with increasing age, with the highest proportional incidence in the 40–49 year age group for first year (56%, 95% confidence interval [CI] 50–62%) and second-year (86%, 95% CI 82–90%) interval cancers. Proportional incidence for women aged 50–69 years for first- and second-year interval cancers was 31% (95%CI 29–33%) and 50% (95% CI 47–52%) respectively. Sensitivity estimates for the program increased significantly with age, with lowest sensitivity estimates evident for women 40–49 years. In women aged 40–49 years the meta-analysed proportional incidence rate for randomised trials of screening for first- and second-year interval cancers was 42% (95% CI 21–62%) and 63% (95% CI 55–71%) respectively, while for service studies it was 44% (95% CI 31–58%) and 72% (95% CI 51–92%). Proportional incidence in the New South Wales program for women aged 40–49 years was not significantly different to the meta-analysed proportional incidences for trial and service studies in the first year, or for service studies in the second year. Conclusion: Proportional incidence of interval cancer was significantly higher in women aged 40–49 years in New South Wales relative to older age groups, but did not differ significantly from service studies of women in a similar age group. The effectiveness of mammography screening for this age group needs to be examined in view of the comparatively high rate of interval cancers.

Interval breast cancers in New South Wales.

This article describes a study that examined the effectiveness of mammographic screening offered to 50–69 year old women in NSW through BreastScreen NSW in 1996.