Abstract
BackgroundThoracic reirradiation (re-RT) is increasingly administered. However, radiation pneumonitis (RP) remains to be the most common side effect from retreatment. This study aimed to determine the risk and predictors for severe RP in patients receiving thoracic re-RT.MethodsSixty seven patients with lung cancer received thoracic re-RT for recurrent or metastatic disease. Three-dimensional conformal radiotherapy (3D-CRT)/intensity modulated radiotherapy (IMRT) was used for 60 patients, and stereotactic body radiation therapy (SBRT) was used in 7 patients. Deformable image registration (DIR) was performed to create a composite plan. Severe (grade ≥ 3) RP was graded according to Common Terminology Criteria for Adverse Events version 4.0.ResultsEighteen patients (26.9%) developed grade ≥ 3 RP (17 of grade 3, and 1 of grade 4). In univariate analyses, V5 and mean lung dose (MLD) of initial RT or re-RT plans, V5 and V20 of composite plans, and the overlap between V5 of initial RT and V5 of re-RT plans/V5 of re-RT plans (overlap-V5/re-V5) were significantly associated with grade ≥ 3 RP (P < 0.05 for each comparison). Multivariate analysis revealed that MLD of the initial RT plans (HR = 14.515, 95%CI:1.778–118.494, P = 0.013), V5 of the composite plans (HR = 7.398, 95%CI:1.319–41.495, P = 0.023), and overlap-V5/re-V5 (P = 0.041) were independent predictors for grade ≥ 3 RP. Out-of-field failures with medium overlap-V5/re-V5 of 0.4–0.8 was associated with higher risk of grade ≥ 3 RP compared with in-field failures (18.3% vs. 50%, P = 0.014).ConclusionsThe risk of grade ≥ 3 RP could be predicted not only by dose-volume variables from re-RT plan, but also by some from initial-RT and composite plans. Out-of-field failures was associated with higher risk of severe RP compared with in-field failures in some cases.
Highlights
For patients receiving stereotactic body radiation therapy (SBRT), GTV was delineated on a maximal intensity projection of 4-dimensional computed tomography (4D-Computed tomography (CT)) and modified according to its movement to create the internal gross tumor volume, and an expansion of 3–5 mm was added to create a planning target volume (PTV)
FDG-PET/CT was mainly used for the diagnosis of recurrent, metastatic, or new primary lung tumors, and histological confirmation was achieved in 38.8% (26/ 67) of the patients
Rates of grade ≥ 3 radiation pneumonitis (RP) for patients with the largest overlap-V5/re-V5 of 0.8–1 were similar to patients with the smallest overlap-V5/re-V5 of 0–0.4 (18. 3% vs. 14.3%, P = 1.000), but were significantly lower when compared with patients with the medium overlapV5/re-V5 of 0.4–0.8 (18.3% vs. 50%, P = 0.014). These findings suggested that the overlap of volume of lung exposed to low radiation doses between initial RT plans and re-RT plans was associated with the incidence of severe RP, and should be paid more attention when evaluating a plan of re- RT
Summary
Radiation pneumonitis (RP) remains to be the most common side effect from retreatment. The rates of recurrent disease after RT still remain high [1, 2]. For recurrent pulmonary tumors after previous thoracic RT, salvage surgery is typically avoided. Published studies have demonstrated the effectiveness of re-RT for recurrent, metastatic pulmonary tumors, or a new primary lung tumor after previous thoracic RT [6,7,8,9,10,11,12,13,14]. Radiation pneumonitis (RP) remains to be the most common side effect from retreatment, up to 40% in some cases [6, 12, 14]
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