Margriet Kwint

Chapter 7 132 in 24 fractions) for NSCLC patient treated with CCRT (21, 22). As a showcase, the electronic registration of AET was used to validate the applicability of this RWD for the NTCP models of AET for CCRT for NSCLC-patients, for 2 sequential cohorts. Materials and Methods Patient selection A consecutive cohort of patients treated with CCRT for cytologically or histologically proven NSCLC in our institute between 2014 and 2016, were selected for this analysis. The clinical AET grades from the electronic toxicity registration as well as patient characteristics and dose-volume-parameters of the esophagus were available for all patients. Baseline characteristics are presented as mean (+standard deviation (SD)) or median (+ interquartile range) in case of a skewed distribution or proportions. Treatment The concurrent chemotherapy regimen consisted of daily low dose Cisplatin intravenous (6 mg/m²) 1-2h before irradiation. The patients treated between January 2014 until June 2015 were treated with IMRT of 66 Gy to the primary tumor and mediastinal lymph nodes in 24 fractions, once daily, 5 times per week. Since the 1 st of June 2015 the dose on the irradiated mediastinal lymph nodes was de-escalated from 66Gy to 58.08 Gy (60 Gy BED) in 24 fractions (21, 22). Therefore, this dose de- escalation was used as a showcase to audit the quality of the NTCP-models before/ after this treatment adaptation with the use of RWD. Radiotherapy preparation For all patients a 3D-midventilation-CT (MidV-CT) was selected out of a respiration correlated 4DCT, in which the moving tumor was closest to its time-averaged mean position (23). The gross tumor volume (GTV) and all pathological lymph nodes were delineated on the MidV-CT which was also registered with a recent fludeoxyglucose- positron-emission-tomography-(FDG-PET)-scan. The GTV was expanded to a planning target volume (PTV) using a personalized margin protocol based upon the tumor and lymph node movement during breathing. Critical organs were delineated according to a written protocol: heart, spinal cord, lungs and esophagus (from cricoid to gastro-esophageal-junction). The planning-constraints used for the organs at