P2-223: Analysis of clinical and dosimetric factors associated with severe radiation pneumonitis in locally advanced Non–Small–Cell–Lung–Cancer patients treated with concurrent chemotherapy and intensity–modulated radiotherapy (IMRT)

Abstract

To retrospectively evaluate clinical and dosimetric factors associated with severe (grade≥3) radiation pneumonitis in patients after concurrent chemotherapy and intensity-modulated radiotherapy (IMRT). We retrospectively analyzed 94 locally advanced NSCLC patients treated with concurrent chemotherapy and IMRT between May 2005 and September 2006. Radiation pneumonitis was graded according to Common Terminology Criteria for Adverse Events version 3.0. The following clinical parameters were considered: gender, age, smoking and diabetes history, history of chronic obstructive pulmonary disease (COPD), induction chemotherapy, concurrent chemotherapy regimens, performance status and forced expiratory volume in 1 second (FEV1). Dosimetric factors including mean lung dose (Dmean), rV5-V60 relative volumes of lung receiving more than a threshold dose D of radiation (rVD), where values of D considered were 5°C 60 Gy in increments of 5 Gy), prescribed dose (63GY/35f/7w vs 60Gy/30f/6w), and normal tissue complication probability (NTCP) values were analysed. DVHs data and NTCP values were collected for both lungs considered as a parallel organ. Pearson Chi-Square test was performed to compare clinical parameters between patients who developed severe RP and those who did not. Univariate and multivariate logistic regression analyses were performed to evaluate data for association between clinical and dosimetric factors and severe RP. The study was approved by the institutional reviewboard. Of 94 patients, 11 (11.7%) develop severe (grade≥3) radiation pneumonitis; 6 (6.4%), grade 3; 2(2.1%), grade 4; and 3 (3.2%)grade 5. Univariate analyses show that Sex, age (≤60vs>60), smoking and diabetes history, induction chemotherapy, concurrent chemotherapy regimens, PS(≤70vs>70) and prescribed dose did not significantly differ between patients who developed severe RP and those who did not. However, NTCP, MLD, rV5-V60, COPD and FEV1 were associated with severe RP (p<0.05). In multivariate analysis, NTCP (p=0.001) and rV10(p=0.015) was the most significant factors associated with severe (grade≥3) radiation pneumonitis. The incidences of Grade≥3 pneumonitis in the group with NTCP>4.2% and NTCP <4.2% were 43.5% and 1.4%, respectively (p<0.01). The incidences of Grade≥3 pneumonitis in the group with rV10 <51.2% and rV10 >51.2% were 5.6% and 30.4%, respectively (p<0.01). NTCP and rV10 is useful indicator of risk for development of severe (grade≥3) radiation pneumonitis in NSCLC patients after concurrent chemotherapy and intensity -modulated radiotherapy (IMRT).