Jacky Luiten

108 | Chapter 7 as small metastases sized 0.2–2.0 mm), which are of limited prognostic value on disease free and overall survival. 15 Therefore, we agree with a recent study by Van Roozendaal et al. who suggest to omit SLNB completely in patients with DCIS undergoing BCS, as preforming a delayed SLNB following lumpectomy if invasive cancer is shown is nowadays considered a feasible option. 39 In patients undergoing mastectomy, SLNB cannot reliably be performed afterwards and therefore may still need to be performed in DCIS patient undergoing a mastectomy. 9 Our study suggests that many clinicians use DCIS grade not only to consider the use of additional radiotherapy, but also the use of SLNB. Ongoing clinical trials aiming to identify a subgroup of low risk DCIS also base identification of this subgroup on histologic grade. 40,41 DCIS grading is based on morphologic characteristics, such as growth pattern, cytoplasmatic feature, nuclear pleomorphism and mitotic activity. Since diagnostic criteria are not always clear, differences in morphological interpretation do make the accuracy of DCIS grading questionable. 42,43 Consequently, histologic grading of DCIS is currently not meeting high enough standards. 44 Improvement of the accuracy is extremely relevant, since grade is the most important determinant for the management of DCIS at the moment. Recent studies on molecular alteration driving the progression of DCIS towards invasive breast cancer, show that gene expression profiling can possibly improve the ability to predict progression to invasive breast cancer. 45 ‐ 47 This suggests that more effective methods of detecting, diagnosing and treating DCIS can be developed based on targeting these genes, resulting in more individualized treatments in the near future. However, gene expression profiling is still very expensive and recent st udies suggest that the use of a free ‐ of ‐ charge online Nomogram (available online at www.nomograms.org ) is concordant with those obtained using the commercially av ailable DCIS scores for women aged 50 years or older with small DCIS (  2.5 cm). 48 This study has several limitations. The study population, selected from the NCR, was not manually controlled using the PALGA database. A previous study by Elshof et al., also using data from the NCR, has shown that not all DCIS patients in the NCR database consisted of pure DCIS when checked in the PALGA database. 14 Therefore, our results on the iRFS must be interpreted considering this misclassification, especially in the older years, which may have caused a too low iRFS rate. Furthermore, the follow ‐ up in our iRFS analysis for recent years (2011 ‐ 2018) is still short. In addition, the iRFS analysis only contains invasive relapses. Data on non ‐ invasive relapse was not available. Data on overall survival were not included in this study, since it has already been described that DCIS patients have a higher