Jacky Luiten

Patterns of treatment and outcome of ductal carcinoma in situ in the Netherlands | 101 7 underwent BCS and 374 (1.3%) did not receive any surgical treatment (Figure 7.1). The percentage of patients undergoing BCS increased from 47.7% (460/965) in 1995 ‐ 1996 to 72.7% (2,474/3,404) in 2017 ‐ 2018 ( p <0.001). Figure 7.1 Trends in type of surgical treatment. BCS = breast conserving surgery; RTx = radiotherapy. Among patients undergoing BCS, 78.7% (13,859/17,619) received adjuvant radiotherapy. This proportion increased from 28.9% (133/460) in 1995 ‐ 1996 to 89.6% (1,890/2,110) in 2011 ‐ 2012 ( p <0.001) and decreased again to 74.9% (1,854/2,474) in 2017 ‐ 2018 ( p <0.001). Figure 7.2 shows the trend in use of radiotherapy after BCS since 2001, divided by DCIS grade. For low grade DCIS the number of patient receiving adjuvant radiotherapy increased from 41.5% (68/164) in 2001 ‐ 2002 to 77.3% (170/220) in 2007 ‐ 2008 ( p <0.001) which steadily decreased in more recent years to 30.5% (127/416) in 2017 ‐ 2018 ( p <0.001). For intermediate and high grade DCIS, the use of radiotherapy remained rather stable ( p =0.72 and p =0.09 respectively). When comparing use of BCS in the different gradings in 2017 ‐ 2018, 30.5% (127/416) of all low grade DCIS was treated with BCS including adjuvant radiotherapy, compared to 76.7% (758/988) of all intermediate grade DCIS ( p <0.001) and 93.9% (918/978) of all high grade DCIS ( p =0.002).