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

BACKGROUND AND PURPOSE: This 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 METHODS: 62 patients with 407 pulmonary metastases from HCC were consecutively treated with HT. The median radiation dose was a 49.7Gy in 4.0Gy/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).

RESULTS: Univariate 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 3-50Gy (VBED3-50 ) were associated with SRP. Multivariate logistic regression analysis showed that VBED20 and NPML were significant parameters (both P<0.001) CONCLUSIONS: Our findings indicated that SRP can be predicted with NPML>5 and VBED20 ≥30.4% with the α/β ratio of 3Gy.