Jacky Luiten

102 | Chapter 7 Figure 7.2 Trends in the use of radiotherapy after breast conserving surgery divide by grade since 2001. Axillary surgery in DCIS Since 1995, 872 (3.1%; 872/28,357) women underwent ALND. When excluding all missing data since 1995 ( n =437; 1.5%) the proportion of women undergoing ALND decreased over the years from 23.0% (223/1,084) in 1995 ‐ 1996 to less than 1% (27/2,806) in 2009 ‐ 2010 and later ( p <0.001). SLNB was performed in 11,340 women since 2005 (53.5%; 11,340/21,196). The proportion of patients undergoing SLNB rapidly increased since its introduction in 1997 ‐ 1998 to 63.1% (2,328/3,690) in 2013 ‐ 2014 and subsequently decreased to 52.8% (1,888/3,573) in 2017 ‐ 2018 ( p <0.001). Overall, 20.2% (684/3,393) of all patients with low grade DCIS underwent SLNB compared to 45.1% (3,197/7,087) of those with intermediate DCIS and 71.9% (7,031/9,778) of those with high grade DCIS ( p <0.001). Figure 7.3 shows the trend in SLNB use categorized by DCIS grade since 2005. When categorized by type of breast surgery, as shown in Figure 7.4, 75.1% (5,058/6,732) of all patients who underwent a mastectomy since 2005 underwent SLNB, compared to 45.0% (6,270/13,922) of the patients who underwent BCS ( p <0.001). In recent years, an increasing number of patients did not receive any axillary surgery. When focusing on BCS only, 52.3% (6.900 /13.187) of all women did not receive axillary surgery since 2005. In 2013 ‐ 2014 axillary surgery was omitted in 45.6% (1,140/2,498), compared to 55.8% in 2017 ‐ 2018 (1,381/2,474; p <0.001; Figure 7.5).