Margriet Kwint

Chapter 6 118 Where β 0 and β 1 are the estimated coefficients and Vx is the most significant dosimetric parameter. The new model was then compared with the currently used constraint of the V35 [2] using chi-square distribution with 3 degrees of freedom (β 0 , β 1 , Vx) . The dose-volume-parameters of the current IMRT-patients were compared to the historical 3DCRT-data using a 2-sided student t-test. The data was analyzed by SPSS for Windows software, release 15.0 and graphs were generated by Matlab for Windows software, release R2009a. Results Patients Between January 2008 and November 2010, 139 consecutive NSCLC patients treated with IMRT and concurrent chemotherapy were selected ( Table 1 ). Median age was 63 years (range 38-85 years). A total of 109 (78%) patients received all 24 doses of chemotherapy. Due to decreasing renal function (N=20), gastro-intestinal (N=6), hematological (N=2) or cardiovascular (N=2) side effects, the Cisplatin stopped early after 13 up to 23 administrations (mean 19) in 22% of the patients. From the 139 patients the incidences of AET were, 12 (9%), 43 (31%), 53 (38%) and 31 (22%) for grade 0, 1, 2 and 3 AET respectively. No grade 4 and 5 AET was observed. In analogy to the historical data, current AET was increased compared to the historical data for RT-only and SCRT [2] (p<0.0002). The current incidences using IMRT were not significantly different from the historical CCRT data with 3DCRT-treatment (p=0.4832 for AET grade ≥2 and p=0.5457 for AET grade ≥3). Dosimetric variables With the use of IMRT the relative volume of the esophagus receiving dose levels ranging from 5–40 Gy were significantly lower compared to 3DCRT, while the volume receiving 70 Gy was significantly increased ( Figure 1 ). The esophageal V65 turns out to have the highest correlation with AET with a correlation coefficient of 0.300 (p<0.001), although V25-V70, D max and D mean all significantly correlated with AET ( Table 2 ). Additionally, correlations between dosimetric variables (e.g. with V50 shown in Table 2 ) indicate high mutual correlation with each other. This indicates that a wide range of dose-volume-parameters are