Low dose volume of the lung in prediction of acute radiation pneumonitis

Abstract

Objective To observe the incidence of radiation pneumonitis (RP) in patients with non-small cell lung cancer (NSCLC) or esophageal carcinoma treated by three-dimensional conformal radiation therapy (3DCRT), and investigate the predictive value of low dose volume of the lung on RP.Methods From Mar 2005 to Aug 2008, 161 patients with locally advanced NSCLC or esophageal carcinoma received 3DCRT. Fifty-three patients with NSCLC received radiotherapy of 60 Gy/30 -34 fx and concurrent chemotherapy of navelbine plus cisplatin (NP). Among the 108 patients with esophageal carcinoma with prescription doses ranging from 58 Gy/29 fx to 70 Gy/35 fx, 46 and 62 received 3DCRT alone or 3DCRT with concurrent chemotherapy of calcium folinate, 5-Fu and cisplatin (LFP), respectively. Univariate and multivariate analysis and receiver operating characteristics (ROC) curves were performed to assess the correlated factors of RP. Results The follow-up rate was 100%. The rate of RP was 57. 8% (93/161) for all patients, 94% (50/53,including 1 with Grade 4 and 1 with Grade 5) for patients with NSCLC, and 39.8% (43/108, none with Grade 4 and 5) for patients with esophageal carcinoma. The correlative factors included the sex, volume of gross tumor volume (GTV), mean lung dose (MLD), V5, V10, V15, V20, V25 and V30 of normal lung according to Spearman correlative analysis. Univariate analysis showed that all the 9 factors could predict RP. Only V5 and the volume of GTV were found independently associated with Grade 2 or more RP in multivariate analysis. ROC analysis indicated that the cut-off point of the curve was 55% with the area under ROC curve of 0. 684 (P = 0. 000). For the patients with lung V5 ≥ 55% and < 55% ,43% (36/84) and 18% (14/77) developed RP of Grade 2 or more, respectively. Conclusions Dosimetric parameters including MLD, normal tissue complication probability, and V5-V30 could predict RP. V5 may be the most valuable predictor. When V5 exceeds 55%, the probability of RP of grade 2 or more may increase notably. Besides the limitation of MLD, V20 and V30, the volume of low dose region should be also limited to a lower range during treatment planning. Key words: Lung neoplasms/radiotherapy; Esophagus neoplasms/radiotherapy; Radiotherapy,three-dimensional conformal; Radiation pneumonitis