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Open Access Highly Accessed Research article

Breast cancer incidence and overdiagnosis in Catalonia (Spain)

Montserrat Martinez-Alonso12, Ester Vilaprinyo3, Rafael Marcos-Gragera45 and Montserrat Rue12*

Author Affiliations

1 Basic Medical Sciences Department, Biomedical Research Institut of Lleida (IRBLLEIDA), Alcalde Rovira Roure 80, Lleida, 25198, Catalonia, Spain

2 Basic Medical Sciences Department, University of Lleida, Montserrat Roig 2, Lleida, 25008, Catalonia, Spain

3 Evaluation and Clinical Epidemiology Department, Hospital del Mar-IMIM, Doctor Aiguader 88, Barcelona, 08003, Catalonia, Spain

4 Epidemiology Unit, Girona Cancer Registry, Passatge Farinera Teixidor 1, Girona, 17005, Catalonia, Spain

5 Catalan Cancer Plan, ICO-Hospital Dr. Josep Trueta, Av. França s/n, Girona, 17007, Catalonia, Spain

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Breast Cancer Research 2010, 12:R58  doi:10.1186/bcr2620

Published: 3 August 2010

Abstract

Introduction

Early detection of breast cancer (BC) with mammography may cause overdiagnosis and overtreatment, detecting tumors which would remain undiagnosed during a lifetime. The aims of this study were: first, to model invasive BC incidence trends in Catalonia (Spain) taking into account reproductive and screening data; and second, to quantify the extent of BC overdiagnosis.

Methods

We modeled the incidence of invasive BC using a Poisson regression model. Explanatory variables were: age at diagnosis and cohort characteristics (completed fertility rate, percentage of women that use mammography at age 50, and year of birth). This model also was used to estimate the background incidence in the absence of screening. We used a probabilistic model to estimate the expected BC incidence if women in the population used mammography as reported in health surveys. The difference between the observed and expected cumulative incidences provided an estimate of overdiagnosis.

Results

Incidence of invasive BC increased, especially in cohorts born from 1940 to 1955. The biggest increase was observed in these cohorts between the ages of 50 to 65 years, where the final BC incidence rates more than doubled the initial ones. Dissemination of mammography was significantly associated with BC incidence and overdiagnosis. Our estimates of overdiagnosis ranged from 0.4% to 46.6%, for women born around 1935 and 1950, respectively.

Conclusions

Our results support the existence of overdiagnosis in Catalonia attributed to mammography usage, and the limited malignant potential of some tumors may play an important role. Women should be better informed about this risk. Research should be oriented towards personalized screening and risk assessment tools.