Margriet Kwint

Intra anatomical changes during radiotherapy 77 4 Characteristic No patients (N=177) % RT-schedule 24x2.75 Gy 113 64 17x3 Gy 31 18 25x2 Gy 25 14 30x2 Gy 3 1.5 30x2.25 Gy 2 1 30x1,5 Gy (2 times a day) 1 0.5 25x1.8 Gy 1 0.5 33x2 Gy 1 0.5 Intra thoracic anatomical changes ITACs were observed in 128 patients (72%). In total 200 ITACs were scored ( Table 2 ). Sixty patients (47%) had 1 ITAC, 46 patients (36%) 2 ITACs and in 22 patients (17%) >2 ITACs were observed. The highest ITAC scored per patient was level red, orange and yellow in 12%, 36% and 24% respectively. 28% off the patients had no observed ITACs (level green). Sixteen patients (9%) required an adapted treatment plan to account for the changed anatomy, for which 14 received a new plannings-CT-scan (8%). It took 1 to 3 working days to generate and implement the adapted plan (mean 2.2 working days). Most ITACs occurred in the first week (55%). In week 2, 3, 4 and 5, in 16%, 15%, 8% and 6% ITACs were observed respectively. Types of ITACs scored were evident regression (35%), tumor baseline shift (27%), changes in atelectasis (19%), tumor progression (10%), pleural effusion (6%) and infiltrative changes (3%) (total N=210 ITACs in 177 patients). The incidence of ITACs was higher in the CCRT- (77%) and SeqCRT-group (74%) compared to the RT-group (52 %) (p=.265). Similarly, the incidence of level red changes was higher in the CCRT- (16%) and SeqCRT-group (12%) compared to the RT-group (0%) (p=.204). In 28(16%) patients atelectasis developed (N=16) or increased (N=12). This occurred mainly in the first week (N=25, 89%). In the other 3 patients atelectasis developed in week 2 (N=2) or week 3 (N=1). These ITACs had mostly level red (N=10, 36%) and level orange (N=15, 53%), the other 3 (11%) were level green. Decrease or resolving of atelectasis occurred in 12 patients (7%). This ITAC was not typically scored in a specific week; N=3 in week 1 and 2 (25%), N=5 in week 3 (42%) and N=1 in week 5 (8%). Level red was observed in 5 patients (42%), level orange in 4 patients (33%) and level yellow in 3 patients (25%).