Jacky Luiten

Patterns of treatment and outcome of ductal carcinoma in situ in the Netherlands | 97 7 Introduction Ductal carcinoma in situ (DCIS) is defined as an intraductal neoplastic proliferation of cells. 1 In most cases, DCIS of the breast are associated with the presence of suspicious calcifications on mammography. Calcifications are the result of precipitations of calcium ‐ salts in intraluminal secretions or necrosis of epithelial cells. 2 The nation ‐ wide biennial mammographic screening program in the Netherlands for women aged 50 ‐ 70 years was set up between 1989 and 1996. In 1999, the upper age limit was extended to 75 years. The program led to a sharp increase in the detection rate of DCIS, which was reinforced by the replacement of screen ‐ film mammography by full ‐ field digital mammography in 2009 ‐ 2010. 3,4 Autopsy studies have shown that DCIS often does not progress to invasive disease. 5 Sometimes a fraction of all preclinical DCIS may even regress spontaneously. 6 The aforementioned implies that part of the observed increase in the diagnosis and treatment of DCIS may be partly unnecessary and could be seen as overdiagnosis, thereby resulting in avoidable treatment ‐ related morbidity. 7,8 However, predicting which DCIS lesions will regress and which will proceed to invasive breast cancer is hardly possible yet. Therefore, almost all patients with DCIS undergo surgical treatment. According to the guidelines, adequate treatment of DCIS consists of mastectomy or breast conserving surgery (BCS), pursuing complete microscopic tumor excision. In case of BCS additional whole ‐ breast radiotherapy is standard of care. 9,10 The recommendation for adjuvant radiotherapy is based on the results of several randomized controlled trials, showing a reduction of the incidence of both in situ and invasive local recurrence by half. 11 ‐ 13 Fifteen ‐ year ipsilateral local recurrence rates following BCS with adjuvant radiotherapy for DCIS vary between 7% and 11%. 14 Contralateral invasive breast cancer incidence fifteen ‐ years after DCIS diagnosis was approximately 6.5%, compared to 3.4% in the general population. 14 There is no evidence which supports performing SNB in patients with pure DCIS in final pathology. 15 Axillary lymph node dissection (ALND), which used to be the gold standard, was therefore replaced by sentinel lymph node biopsy (SLNB) in the late 1990s. Today SLNB for patients with DCIS may be considered in the presence of clinical risk factors for an invasive component or for those who will undergo mastectomy. 16 The aim of this population ‐ based study was to evaluate patterns of care in the treatment of DCIS in the Netherlands since the introduction of the national screening program with particular interest in the use of BCS, radiotherapy