A prospective study on radiation pneumonitis following conformal radiation therapy in non-small-cell lung cancer:: clinical and dosimetric factors analysis

Background and purpose: Clinical and dosimetric prognostic factors for radiation pneumonitis (RP) have been reported after three-dimensional conformal radiotherapy (3D-CRT) in patients with non-small cell lung cancer (NSCLC). Patients and methods: Ninety-six patients who received 3D-CRT for stage IA to IIIB NSCLC were evaluated prospectively. Surgery was performed before radiation in 51 % of the patients (n = 49). RP was diagnosed six-eight weeks after 3D-CRT using the Lent-Solna classification. Factors evaluated included treatment factors such as total mean lung dose (MLD), and dose-volume histogram (DVH) thresholds for several radiation dose steps. These thresholds were originally determined from the median of the irradiated lung volume at each step. Results: Six patients could not be evaluated for RP six weeks after 3D-CRT. Of the 90 remaining patients, 40 (44%) had RP (i.e. grade greater than or equal to 1) at 6 weeks, including 7 patients (7.8%) with severe RP (grade greater than or equal to 2). Regarding the whole toxicity (grade greater than or equal to 1), age ( greater than or equal to 60 years), MLD, V20 and V30 were significantly related to RP. DVH thresholds determined for radiation doses from 20 to 40 Gy were also predictive of RP. Considering only severe RP (grade greater than or equal to 2), only MLD, V20 and V30 remained associated with increased acute pulmonary toxicity. Conclusions: In this study, dosimetric factors (MLD, V20, V30) and age ( greater than or equal to60 years) were predictive of RP regarding the whole pulmonary toxicity (grade greater than or equal to 1). In addition, thresholds from 20 to 40 Gy, based on a stratification according to the median of the percentage of irradiated lung volume, were also predictive factors. They may, therefore, help discriminate patients at high and low risk for RP. However, only MLD, V20 and V30 remained associated with severe RP (grade : 2), probably due to the small number of severe events in our series. (C) 2004 Elsevier Ireland Ltd. All rights reserved.