Evaluating risk factors of radiation pneumonitis after stereotactic body radiation therapy in lung tumor: Meta-analysis of 9 observational studies

BackgroundIn this study, we assessed the association of SBRT (stereotactic body radiotherapy) dose and volume with radiation pneumonitis (RP) risk in lung tumor.MethodsRelevant articles were identified up to April 2018, using following databases; Medline, EMBASE, Cochrane Library, and China National Knowledge Infrastructure (CNKI). The pooled OR (odds ratio) with 95% CI (confidence interval) data [mean ± SD (standard deviation)] obtained from different studies was analyzed by statistical analysis using a fixed-effects model or a random-effects model when appropriate.ResultsThe analysis was based on nine observational studies, which were identified based on the study selection criteria. Between RP and non-RP patients, no difference was observed based on age, but significant differences were observed based on planning target volume (PTV), mean ipsilateral lung dose (MLD), total MLD, and V5, V10, V20 and V40 (the percentage of lung volume exceeding 5, 10, 20 and 40 Gy). In addition, PTV >145 cm3, total MLD ≥4.7 Gy, V5 ≥26.8%, V10 >12% and V20 ≥5.8 were associated with RP risk. Overall, the grade assessments of V5 and V20 revealed moderate quality evidence.ConclusionThe present study indicated V5 and V20 as major risk factors for RP after SBRT treatment in lung tumor. In addition, it was observed that lung DVH (Dose Volume Histogram) patterns should be assessed more carefully, while predicting RP incidence after SBRT.

**背景**：本研究旨在评估肺肿瘤患者接受立体定向体部放疗（SBRT, stereotactic body radiotherapy）时，放疗剂量与体积参数和放射性肺炎（RP, radiation pneumonitis）发病风险之间的关联。**方法**：本研究检索截至2018年4月的相关文献，检索数据库包括Medline、EMBASE、Cochrane图书馆及中国知网（CNKI, China National Knowledge Infrastructure）。针对从各项研究中提取的合并比值比（OR, odds ratio）、95%置信区间（CI, confidence interval）数据以及均值±标准差（SD, standard deviation），采用固定效应模型或适宜情况下的随机效应模型进行统计学分析。**结果**：本分析共纳入符合研究纳入标准的9项观察性研究。放射性肺炎患者与非放射性肺炎患者的年龄无显著差异，但在计划靶体积（PTV, planning target volume）、患侧肺平均剂量（MLD, mean ipsilateral lung dose）、总平均肺剂量（total MLD）以及V5、V10、V20、V40（即肺组织接受剂量超过5、10、20、40Gy的体积百分比）方面存在显著差异。此外，PTV＞145cm³、总平均肺剂量≥4.7Gy、V5≥26.8%、V10＞12%及V20≥5.8均与放射性肺炎发病风险相关。整体而言，针对V5与V20的分级评估证据质量为中等。**结论**：本研究表明，V5与V20是肺肿瘤患者接受立体定向体部放疗后发生放射性肺炎的主要危险因素。此外，在预测立体定向体部放疗后放射性肺炎的发病风险时，应更为细致地评估肺剂量体积直方图（DVH, Dose Volume Histogram）特征。