43.25 33.97 24.28 15.47 10 20 40 50 60 66.33 54.93 40.21 15.14 30 Gy 7.38 30 Gy The analysis of prognostic factors affecting post-radiation acute reaction after conformal radiotherapy for non-small cell lung cancer 5.07 2.97 1.32 10 20 40 50 60 49.52 29.86 20.98 16.11 11.16 6.80 Results Fifty-three percent of patients included in the study suffered from acute post-radiation pneumonitis. Fifteen (44.1%) patients experienced grade 2, and 3 (8.9%) patients grade 3 toxicity according to the modified RTOG/EORTC scale. No grade 4 toxicity was recorded in this study. All patients with grade 3 lung toxicity required hospitalization and intensive medical care. The mean time to clinical manifestation of acute post- radiation reaction in patients who experienced post- radiation pneumonitis was 5.3 weeks (min 2.7 weeks; max 16 weeks, median 7.4; 95% CI 4.2-8.7 weeks). In all patients except 2, acute post-radiation pneumonitis revealed itself before the end of the third month after the end of radiotherapy. In these 2 patients the acute post-radiation pneumonitis occurred at weeks 13 and 16 after the end of treatment. The mean volumes of lung tissue which received doses in the range of 10-60 Gy in the analysed group are presented in Figure 1. A-C. Clinical factors including age, sex, tumour size, clinical stage, Karnofsky Performance Status, use of induction chemotherapy, and haemoglobin concentration before radiotherapy did not have any impact on acute lung toxicity risk (p ≥ 0.18). The analysis of dose-volume histograms showed a difference in lung volumes receiving low doses (10 Gy, 20 Gy) in groups of patients with and without clinical manifestation of the side effect (p ≤ 0.01). The mean ipsilateral lung volume receiving 10 Gy in patients with post-radiation pneumonitis was 70.37%, and only 57.22% in patients without clinical manifestation of this acute side effect (p = 0.002). Also differences of mean contralateral and total lung volume, in both groups of patients, with and without clinical manifestation of post-radiation pneumonitis, were statistically significant, at a dose level of 10 Gy. These differences were 46.04% vs. 31.44% for contralateral lung and 56.73% vs. 38.68% for total lung volume respectively (p = 0.011; p < 0.001). Statistically significant mean volume differences of ipsilateral lung tissue, contralateral and total lung volume were demonstrated for a 20 Gy dose as well. Differences in both groups of patients with and without clinical manifestation of post-radiation pneumonitis were 58.16% vs. 47.66% for ipsilateral lung (p = 0.007). For contralateral and total lung volume these differences were respectively 17.91% vs. 10.00% and 36.14% vs. 12.41% (p = 0.016; p < 0.001). For lung tissue receiving higher doses, in the range of 30–60 Gy, statistically significant differences were observed in total lung volume only. For the dose of 30 Gy the difference was 25.23% vs. 14.59% (p < 0.001), and 19.28% vs. 11.36% for the dose level of 40 Gy (p < 0.001). For the 50 Gy and A 80 70 lgnu60 l a r ltea 50 i s p i fo40 e m u lvo 30 % 20 10 0 45 g n llau 35 r e t a l r t con 25 f o e m u lvo 15 % 5 B C 60 50 e lum40 o v g n llau30 t o t % 20 10 0 30 Gy 10 20 40 50 60 Mean ±0.95 CI Figure 1. The relationship between lung tissue mean volumes and absorbed doses in the range of 10-60 Gy. A – ipsilateral lung; B – contralateral lung; C – total lung volume Arch Med Sci 5, October / 2010 759