Analysis and classification of interval cancers in a French breast cancer screening programme (departement of Isere)

The objective of this study is to analyse detection rates and stage of diag nosis of interval cancers in the mass screening mammography programme of Is ere (France), launched in 1990, Interval cancers are defined as breast canc ers diagnosed within 30 months after a negative screening assessment, for w omen attending the programme between November 1990 and December 1994, Stage s of diagnosis of these cancers are compared with those of screened cancers and to those of cancers diagnosed outside the programme. The rates of inva sive interval cancers are 17.7% of the expected incidence rate during the f irst year, 60.0% during the second year and 58.8% after the second year. Se nsitivity of the programme (one test every 30 months) is 74%; sensitivity a t one year is 82%, Results are better for women aged 60-69 years than for y ounger women (50-59 years). Diagnosis is made at an early stage with 8% of in situ cases, and with 40% of very small tumours (sizes less than or equal to 10 mm). Those stages are very close to the ones for screened cases, Int erval cancer rates are low during the first year. Higher rates for the seco nd year and early stages of diagnosis could be explained by self-referred s creening practice in our area. (C) 1999 Lippincott Williams & Wilkins.