Effects of different phases of an invitational screening program on breast cancer incidence

Abstract

The aim of this study was to quantify the effects of separate phases of an invitational screening program on breast cancer incidence at different ages. Our database included detailed municipality-specific information about invitations for mass-screening for breast cancer in 267 Finnish municipalities from time period 1987-2001. The age range was 50-74. For this study, the program was divided into 7 separate phases, and those that had not been invited served as a baseline. The incidence rate was modeled using Poisson regression. To study the differences between age groups within each program phase, an interaction term between age group and phase of screening was included in the model. The modeling was done separately for localized breast cancers, nonlocalized breast cancers and all stages combined. For localized cancers, the risk compared to the noninvited increased during the first years of the 2-year screening rounds in all age groups, and declined below the baseline during the second years. This effect was larger during the first round compared to the subsequent ones. In nonlocalized cancers, a clear incidence peak was detected only during the first year of the first round. A decreasing post screening effect was detected in nonlocalized cancers in women aged 60-69, but not in localized cancers. Cumulating over ages 50-74, extra incidence caused by regular screening in localized cancers was 5.2% if the program was continued up to age 59, and 28.0% if it continued up to age 69. Corresponding figures for nonlocalized cancers were decreases of 19.8% and 20.9%, respectively. ' 2006 Wiley-Liss, Inc.Key words: incidence; breast cancer; mass-screening; mammography Regular mass-screening has been shown to have an impact on breast cancer incidence. [1][2][3][4][5][6][7][8][9][10] There is, however, a little information on how the separate phases of an invitational program differ from each other in terms of influencing the incidence. 1-3 It is also reasonable to assume that the impact of different program phases on breast cancer incidence is dependent on women's age and stage of cancer, which are issues that have, to our knowledge, never been studied jointly before.Møller et al. have estimated the influence of invitational screening program phases on breast cancer incidence by assuming that each municipality within a country follows the same, fixed massscreening pattern given by official recommendations. 1,2 In the study of Jonsson et al., starting times, age range and screening intervals of the included programs were collected by a questionnaire. 3 Our access to a database that includes actual year-and agespecific screening invitation information from Finnish municipalities makes it possible to take into account the real patterns of screening in the municipalities. It also makes it possible to study and code adequately the different phases of the 2-year massscreening cycle and to separate the years within a screening round from each other. As a result, we expect more accurate and detailed information about the impacts o...

Overdiagnosis by mammographic screening for breast cancer studied in birth cohorts in The Netherlands

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Complexities in the estimation of overdiagnosis in breast cancer screening

“…The recent decline was mostly attributed to a lower prevalence of hormone replacement therapy (HRT) use (Ravdin et al, 2007), whereas the levelling off of screening mammography rates in the late 1990s has been suggested as contributing (Glass et al, 2007). In relation to increased incidence in the 1990s, this is usually attributed to the introduction of mammographic screening (Jonsson et al, 2005;Seppänen et al, 2006). It is well established that this causes an immediate rise in incidence, mainly due to the early diagnosis of a many prevalent asymptomatic cancers (Jonsson et al, 2005;Svendsen et al, 2006).…”

Performance and effectiveness of organised breast cancer screening in Finland

“…In the Netherlands, the stage II+ level was met , and a later report showed a clear decline in the rates of advanced cancers after the start of screening ). Recent studies from Finland, too, have reported a decrease in the post screening incidence of non-localised breast cancers (Seppanen et al 2006, Anttila et al 2008. Reduction in the rates of node positive tumours, tumours more than two centimetres in diameter, and stage II+ tumours in the screening era compared to those in the prescreening era have been reported in Sweden (SOSSEG 2007).…”