title: Significant improvement in breast cancer survival through population-based mammography screening.
abstract: The purpose of this study was to evaluate the effect of population-based mammography screening on survival. A total of 176 908 screening examinations were performed in 36 000 women aged 40-74 during the years 1987-1997. Screen-detected and interval primary invasive breast cancers (n=685, screened) were more often smaller (P<0.0001), localised (P<0.0001) and histologically better differentiated (grade I vs II-III, P<0.0001) than pre-screening cancers and cancers detected after the defined interval from the last screening (n=184, clinical). Survival was far better in the "screened" group than in the "clinical" group (P<0.0001, HR 2.55; CI 95% 1.77-3.67). Cox's multivariate analysis revealed axillary lymph node negativity (P<0.0001), histological grade I (P=0.0005) and size less than or equal to 20mm (P=0.0118) as explanations of the beneficial effect of screening. A new observation we recorded was that screening had a beneficial effect even in women whose cancer had already spread into the axillary lymph nodes.
authors.affiliation: Department of Pathology, Turku University Hospital, FIN-20520 Turku, Finland. pekka.klemi@tyks.fi
authors.forename: Pekka J
authors.initials: PJ
authors.lastname: Klemi
authors.forename: Ilmo
authors.initials: I
authors.lastname: Parvinen
authors.forename: Liisa
authors.initials: L
authors.lastname: Pylkkänen
authors.forename: Lea
authors.initials: L
authors.lastname: Kauhava
authors.forename: Pirjo
authors.initials: P
authors.lastname: Immonen-Räihä
authors.forename: Osmo
authors.initials: O
authors.lastname: Räsänen
authors.forename: Hans
authors.initials: H
authors.lastname: Helenius
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000401:mortality*; D016001:Confidence Intervals; D005260:Female; D005387:Finland; D006801:Humans; D008327:Mammography / Q000706:statistics & numerical data*; D008403:Mass Screening / Q000592:standards* / Q000639:trends; D008875:Middle Aged; D009367:Neoplasm Staging; D011159:Population Surveillance; D011237:Predictive Value of Tests; D011336:Probability; D011379:Prognosis; D016016:Proportional Hazards Models; D018570:Risk Assessment; D016019:Survival Analysis