Abstract
Background: This study aims to establish lung biologically effective dose (BED)–based uniform dosimetric constraints for minimizing the risk of symptomatic radiation pneumonitis (SRP) from stereotactic body radiation therapy (SBRT) using variable fractionations in patients with lung tumors.Materials and Methods: A total of 102 patients with primary or oligometastatic lung tumors treated with SBRT in our institution were enrolled into this study. The associations between the clinical and dosimetric parameters and the incidences of SRP were analyzed using univariate and multivariate Cox regression hazard models. The receiver operating characteristic (ROC) curve was generated to evaluate the predictive performance of lung BED on the SRP risk compared with the physical dose.Results: SRP occurred in 11 patients (10.8%). In univariate analysis, the mean lung dose (p = 0.002), V5 (p = 0.005), V20 (p < 0.001), and the percentage of non-target normal lung volume receiving more than a BED of 5–170 Gy (VBED5−170, p < 0.05) were associated with SRP. Multivariate logistic regression analysis showed that there existed a significant statistical correlation between SRP and VBED70 (p < 0.001), which performed better than V5 or V20 on the ROC curves, resulting in an optimal cut-off value of lung VBED70 of 2.22%.Conclusions: This retrospective study indicated that non-target lung BED may better predict SRP from patients with SBRT-treated lung cancer. Limiting the lung VBED70 below 2.22% may be favorable to reduce the incidence of SRP, which warranted further prospective validation.
Highlights
Surgical resection still remains the standard of care for patients with operable early-stage non-small cell lung cancer (NSCLC)
Hypofractionated stereotactic body radiation therapy (SBRT) has dramatically improved the management of inoperable early-stage NSCLC and oligometastatic pulmonary diseases with excellent tumor control and overall survival in comparison with conventional radiotherapy [3, 16]
In contrast to conventional radiotherapy routinely used for locally advanced NSCLC in combination with chemotherapy, SBRT delivers highly focused, high fractionated dose to a limited target volume, typically smaller than 5 cm in diameter with the mediastinal structures spared
Summary
Surgical resection still remains the standard of care for patients with operable early-stage non-small cell lung cancer (NSCLC). For those patients with inoperable conditions, the hypofractionated stereotactic body radiation therapy (SBRT) can achieve better outcomes than conventional radiation therapy, and even comparable efficacy with surgery in terms of local control and overall survival [1, 2]. Mounting evidence has shown that the incidence rate of RP could be higher than 50%, and the percentage of symptomatic RP (SRP, grade ≥2 RP) ranges from 9 to 28% [4]. This study aims to establish lung biologically effective dose (BED)–based uniform dosimetric constraints for minimizing the risk of symptomatic radiation pneumonitis (SRP) from stereotactic body radiation therapy (SBRT) using variable fractionations in patients with lung tumors
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