Association of volumetric-modulated arc therapy with radiation pneumonitis in thoracic esophageal cancer

The lung volume receiving low-dose irradiation has been reported to increase in volumetric-modulated arc radiotherapy (VMAT) compared with three-dimensional conformal radiotherapy (3DCRT) for thoracic esophageal cancer, which raises concerns regarding radiation pneumonitis (RP) risk. This single institutional retrospective cohort study aimed to explore whether VMAT for thoracic esophageal cancer was associated with RP. Our study included 161 patients with thoracic esophageal cancer, of whom 142 were definitively treated with 3DCRT and 39 were treated with VMAT between 2008 and 2018. Radiotherapy details, dose–volume metrics, reported RP risk factors and RP incidence were collected. The RP risk factors were assessed via multivariate analysis. Dose–volume analysis showed that VMAT delivered more conformal dose distributions to the target volume (P < 0.001) and reduced V(30 Gy) of heart (57% vs 41%, P < 0.001) but increased V(5 Gy) (54% vs 41%, P < 0.001) and V(20 Gy) (20% vs 17%, P = 0.01) of lungs compared with 3DCRT. However, the 1-year incidence rates of RP did not differ between the two techniques (11.3% in 3DCRT vs 7.7% in VMAT, P = 0.53). The multivariate analysis suggested that the presence of interstitial lung disease (ILD) (P = 0.01) and V(20 Gy) of lungs ≥20% (P = 0.008) were associated with RP. Conclusively, VMAT increased the lung volume receiving low to middle doses irradiation, although this might not be associated with RP. Further studies are needed to investigate the effect of using VMAT for delivering conformal dose distributions on RP.