Jacky Luiten

Patterns of treatment and outcome of ductal carcinoma in situ in the Netherlands | 107 7 Four randomized controlled trials on adjuvant radiotherapy in DCIS patients have been published. 11,12,26,27 An overview of these trials showed that additional radiotherapy halves the risk of an ipsilateral breast event (invasive and non ‐ invasive). However, it has not been shown to improve breast cancer overall survival. 28 If no survival benefit is found, the reduced risk of local recurrence following radiotherapy must be weighed against the disadvantages. The most common side effect of radiation is acute skin toxicity within weeks after treatment. Radiation can also have negative cosmetics effects due to development of skin pigmentation, telangiectasia, fibrosis and retraction. 29 Furthermore, breast radiotherapy might increase the risk of primary lung cancer among smokers and left ‐ sided breast cancer radiotherapy is proven to be cardiotoxic. 30,31 Because of this long ‐ term side effect the average mean heart dose of left ‐ sided whole breast radiotherapy, which used to be 5.4 Gray 32 , is much lower nowadays with the use of deep inspiration breath hold technique (reduction of 3.4 Gray) and partial breast irradiation. 33 Over the years, research focused on the identification of subgroups of patients with favorable features for whom the risk of invasive recurrence in the absence of radiotherapy is so low that radiotherapy can safely be omitted. 34 A recent observational study in 2016 suggests a possible survival benefit of radiotherapy, which may be most important when certain risk factors are present. 35 Factors such as tumor size, age and nuclear grade were used to produce a recurrence risk scoring system, known as the patient prognostic score. Significant improvements in survival after radiotherapy were only observed in patients with higher nuclear grade, younger age, and larger tumor size. The magnitude of the survival difference with radiotherapy was significantly correlated with this prognostic score ( p <0.001). 35 Therefore, it is recommended to tailor radiotherapy on patient factors, tumor biology and the prognostic score. 35,36 Since pure DCIS is not accompanied by nodal involvement, de ‐ escalating axillary treatment in DCIS patients is justified. ALND is no longer part of the standard treatment for DCIS, as is also illustrated by our study, showing a replacement of ALND by SLNB. In most recent years we also observed a significant declined in axillary staging by any surgical procedure. The trend to omit SLNB is probably initiated by the rather low incidence of SLN involvement, ranging from 0 to 10% between different studies. 37 ‐ 39 Unfortunately, we were not able to report on SLN involvement, as in case of any SLN involvement the diagnosis of DCIS was overwritten by invasive breast cancer in the NCR database. Even if the SLN is found positive in patients with a preoperative diagnosis of DCIS, it is most frequently presents as isolated tumor cells or micrometastases (defined