Pulmonary metastasesConstraints for symptomatic radiation pneumonitis of helical tomotherapy hypofractionated simultaneous multitarget radiotherapy for pulmonary metastasis from hepatocellular carcinoma

Background and purposeThis study was aimed to identify the clinical and dosimetric parameters that predict symptomatic radiation pneumonitis (SRP, radiation pneumonitis ≥ 2 grade) in patients with pulmonary metastasis from hepatocellular carcinoma (HCC) after helical tomotherapy (HT) hypofractionated simultaneous multitarget radiotherapy.Materials and Methods62 patients with 407 pulmonary metastases from HCC were consecutively treated with HT. The median radiation dose was a 49.7 Gy in 4.0 Gy/fraction to 95% of the planning target volume (PTV). The associations between the clinical and dosimetric data and incidences of SRP were analyzed. The dose-pneumonitis relationship was analyzed based on Biologically Effective Dose (BED).ResultsUnivariate analysis showed that the gross tumor volume (GTV), PTV, median lung dose (MLD), the number of pulmonary metastatic lesions (NPML), and the percentage of non-target normal lung (NTNL) volume receiving more than a BED of 3-50 Gy (VBED3-50) were associated with SRP. Multivariate logistic regression analysis showed that VBED20 and NPML were significant parameters (both P < 0.001)ConclusionsOur findings indicated that SRP can be predicted with NPML > 5 and VBED20 ≥ 30.4% with the α/β ratio of 3 Gy.