Safety and outcomes of volumetric modulated arc therapy in the treatment of patients with inoperable lung cancer

Background: Published data on the effects and toxicities of volumetric modulated arc therapy (VMAT) in the management of inoperable lung cancer are scarce. Materials and methods: The clinical outcomes and pulmonary toxicities of 134 patients with consecutive inoperable lung cancer who underwent VMAT from March 2011 to September 2016 were retrospectively reviewed. The dosimetric and characteristic factors associated with acute radiation pneumonitis (RP) and pulmonary fibrosis were evaluated with univariate and multivariate analysis. Results: The average prescription doses to these 134 patients were 57.07±6.27 Gy (range 52-64 Gy). The overall median follow-up time was 18.6 months (range, 2-45 mo), with a median follow-up time for the surviving patients of 20 months (range, 7-45 mo). The 2-year progression-free survival (PFS) and overall survival (OS) for all patients were 18.2% and 38.4%, with a median PFS and OS of 7.6 months and 18.6 months, respectively. The percent of patients with grade III/higher RP and pulmonary fibrosis were 10.5% and 9.0%, respectively. V13 (p=0.02) and age (p=0.02) were independently associated with acute RP according to multivariate analysis. The constraints for lung dosimetric metrics V10,V13,V20 and V30 were approximately 49%,41%,26% and 17% in VMAT treatment of lung cancer to limit the RP rate < 10%. Conclusion: VMAT can be delivered safely with acceptable acute and late toxicities for lung cancer patients. Lung dosimetric metrics were valuable in predicting acute RP. A lung V13 constraint of 40% was helpful to limit the RP rate < 10% in VMAT treatment of lung cancer patients.