Treatment outcome and lung toxicities of volumetric modulated arc therapy in the treatment of inoperable non-small-cell lung cancer patients.

Abstract

e20046 Background: Volumetric-modulated arc therapy (VMAT) has demonstrated the ability to deliver radiation dose precisely and accurately with a shorter delivery time and less MU compared to conventional intensity-modulated fixed-field treatment (IMRT) in the treatment of inoperable non–small-cell lung cancer (NSCLC). However, published data on clinical outcome and lung toxicities of VMAT in the treatment of NSCLC are scarce. Methods: The clinical outcome, acute and late pulmonary toxicities of 134 consecutive inoperable NSCLC patients treated by VMAT with or without concurrent chemotherapy were retrospectively reviewed. Univariate and multivariate analysis on the dosimetric and characteristic factors associated with acute radiation pnuemonitis (RP) and pulmonary fibrosis were evaluated. Results: The average prescriptions dose to these patients were 5736.38±649.11 cGy (range from 5200 to 6400 cGy) with a median follow-up of 18.6 months (range, 2–45 months) for the enrolled 134 patients. The two-year progression-free survival (PFS) and overall survival (OS) for all patients was 18.2% and 38.4% with a median PFS and OS of 7.6 months and 18.6 months, respectively. There were 14 and 12 out of 134 patients experienced grade III/higher RP (10.45%) and pulmonary fibrosis (8.95%), respectively. Age, chemotherapy exposure, dose prescription, V10, V13, V20 and V30 were significantly associated with acute RP. Dose prescription was related to pulmonary fibrosis. Only V13 (p = 0.02) and age (p = 0.02) were independently associated with acute RP according to multivariate analysis. Based on regression analysis, the threshold for lung dosimetric metrics V10,V13,V20 andV30 were 50%,40%,28% and 18% in VMAT treatment of NSCLC to limit the RP rate < 10%. Conclusions: VMAT can be delivered safely with acceptable acute and late toxicities for NSCLC. Lung dosimetric metrics were valuable in predicting acute RP. A threshold of 40% of Lung V13 in VMAT treatment of NSCLC was helpful to limit the RP rate < 10%.