Predicting radiation pneumonitis after radiotherapy or chemoradiotherapy for oesophageal cancer: a single-center retrospective analysis

Background: Multimodality therapy for oesophageal cancer (EC) can cause a variety of treatment-related sequelae, especially pulmonary toxicities. The accurate prediction of radiation pneumonitis（RP）is essential to facilitate individualized radiation dosing that leads to maximized therapeutic gain. In this study, we performed a retrospective analysis to determine important factors that predict RP after radiotherapy (RT) for thoracic segment EC.Methods: Two hundred and forty-seven patients with locally advanced EC who received RT or chemoradiotherapy（CRT）were enrolled. The factors associated with RP in different grades were analyzed by univariate and multivariate analyses, such as basic pulmonary disease, smoking index(SI), three mainstream RT techniques, and dose-volume histogram(DVH). Results: The median RT dose was 60Gy, and the median follow-up time was 10 months. There were 118 cases of RP in 247 cases of EC patients who underwent RT or CRT. Among them, there were 54 cases of symptomatic pneumonitis (≥2 grade). The overall rate of symptomatic pneumonitis was 21.9%. In terms of RT techniques, there was no significant difference in the incidence of RP among three dimensional conformal radiotherapy (3D-CRT), intensity modulated radiotherapy (IMRT) , and tomography (TOMO) (P>0.05). V5-V40 and MLD were associated with all grades of RP（P<0.05). Target volume, lung volume and their ratio were correlated with the incidence of RP（P<0.05). Among clinical factors, the highest risk of RP（≥3 grade）was in patients > 400 of SI. Chronic obstructive pulmonary disease (COPD) is also related to the occurrence of RP (≥1 grade). In addition, V5 and V40 were an independent risk factor for RP grade≥1 (AUC 55.74%, 4.13%). MLD was an independent risk factor for RP grade≥2(AUC 11.91Gy). V5 was an independent risk factor for RP grade≥3 (AUC 57.60%). Conclusions: There was no significant difference in the incidence of RP regardless of radiation therapy technique (3D-CRT, IMRT , and TOMO) and treatment-related factors. SI and COPD are closely related to the occurrence of the corresponding grades of RP. Several lung dosimetric parameters (V5, V40, MLD) may be the most effective predictive factor of RP.