Jacky Luiten

Trends in incidence and tumor grade in screen‐detected DCIS and invasive breast cancer | 17 2 Introduction In the Netherlands, a nation‐wide biennial screening mammography program for women aged 50–70 years has been gradually implemented between 1989 and 1996. In 1999, the upper age limit was extended to 75 years. In the southern part of the Netherlands, screen‐film mammography (SFM) was replaced by full‐field digital mammography (FFDM) in the period from May 2009 to April 2010. 1–3 Over the last decades the incidence of breast abnormalities has increased rapidly. The lifetime incidence of invasive breast cancer and ductal carcinoma in situ (DCIS) increased from 1 out of 12 in the early nineties to 1 out of 7 nowadays. 4 In contrast to invasive breast cancer, DCIS may often be asymptomatic and the increased detection of DCIS is mostly attributed to the use of screening mammography. 5 All women with suspicious abnormalities at screening mammography are recalled to an out‐patient breast unit at hospitals for further analysis. According to current Dutch breast cancer guidelines, all cases of DCIS detected at screening mammography are treated surgically, followed by adjuvant radiotherapy in case of breast conserving surgery. 4 However, autopsy series have shown that a significant part of DCIS stays subclinical during a woman’s lifetime. 6 Therefore overtreatment, caused by the increased detection of DCIS through screening and its subsequent treatment, has become a matter of debate. 7‐9 Moreover, it has been documented that the incidence of screen‐detected DCIS increases more rapidly compared to the incidence of screen‐detected invasive carcinoma. Taking these observations into account one may argue whether the early detection and treatment of DCIS really reflects overtreatment or may lead to a reduction of the development of subsequent invasive breast cancer. The aim of the current study was to analyze the trends in incidence of screen‐ detected DCIS and invasive breast cancers depending on the mammographic techniques and to investigate a possible association between screen‐detected DCIS and screen‐detected invasive breast cancer in large consecutive cohorts over a 10‐year period. Considering the possibility that low grade DCIS may preferably develop into low grade carcinoma and high grade DCIS to high grade carcinoma we investigated the correlation between screen‐detected DCIS and invasive breast cancer classified by grade.