Analysis of proportional incidence and review of interval cancer cases observed within the mammography screening programme in Trento province, Italy.

PURPOSE

The aim of this study was to assess the performance of the mammography screening programme in Trento Province, Italy, by analysing the interval cancers (IC) observed from 2001 to 2008.

MATERIAL AND METHODS

IC were identified by linking screening archives with local cancer registry and pathology archives as well as with hospital discharge records. Proportional incidence was determined according to breast cancers expected in the absence of screening, estimated on the basis of patients/year at risk and age-specific incidence. The review of screening mammograms preceding ICs was performed by an external (three radiologists) and an internal (five radiologists) panel and aimed at assessing the proportion of IC reviewed as screening errors. Results were compared with European Community (EC) recommended standards.

RESULTS

IC proportional incidence was 15.90% for the first year (EC standard <30%) and 25.77% for the second year (EC standard <50%) of the interval. At external review, 18.4% of cases were reviewed as screening errors (identified by at least two of three reviewers), whereas at internal review (identified by at least three of five reviewers) it was 17.4% (EC standard <20%). No significant difference was observed between external and internal review (mean recall rate 8.3% vs. 9.0%; mean identification rate 19.7% vs 19.6%).

CONCLUSIONS

The study confirms good performance of the mammography screening programme in Trento Province, Italy. Comparable results of external and internal reviews suggest that the latter, no doubt easier to be implemented, might be adopted as a routine procedure to assess this early efficacy indicator.