Predicting Radiation Pneumonitis After Stereotactic Ablative Radiation Therapy in Patients Previously Treated With Conventional Thoracic Radiation Therapy

Abstract

Purpose To determine the incidence of and risk factors for radiation pneumonitis (RP) after stereotactic ablative radiation therapy (SABR) to the lung in patients who had previously undergone conventional thoracic radiation therapy. Methods and Materials Seventy-two patients who had previously received conventionally fractionated radiation therapy to the thorax were treated with SABR (50 Gy in 4 fractions) for recurrent disease or secondary parenchymal lung cancer (T <4 cm, N0, M0, or Mx). Severe (grade ≥3) RP and potential predictive factors were analyzed by univariate and multivariate logistic regression analyses. A scoring system was established to predict the risk of RP. Results At a median follow-up time of 16 months after SABR (range, 4-56 months), 15 patients had severe RP (14 [18.9%] grade 3 and 1 [1.4%] grade 5) and 1 patient (1.4%) had a local recurrence. In univariate analyses, Eastern Cooperative Oncology Group performance status (ECOG PS) before SABR, forced expiratory volume in 1 second (FEV1), and previous planning target volume (PTV) location were associated with the incidence of severe RP. The V10 and mean lung dose (MLD) of the previous plan and the V10-V40 and MLD of the composite plan were also related to RP. Multivariate analysis revealed that ECOG PS scores of 2-3 before SABR (P=.009), FEV1 ≤65% before SABR (P=.012), V20 ≥30% of the composite plan (P=.021), and an initial PTV in the bilateral mediastinum (P=.025) were all associated with RP. Conclusions We found that severe RP was relatively common, occurring in 20.8% of patients, and could be predicted by an ECOG PS score of 2-3, an FEV1 ≤ 65%, a previous PTV spanning the bilateral mediastinum, and V20 ≥30% on composite (previous RT + SABR) plans. Prospective studies are needed to validate these predictors and the scoring system on which they are based.

Clinical outcome and predictors of survival and pneumonitis after stereotactic ablative radiotherapy for stage I non-small cell lung cancer

“…Reports of dose-volume analyses in SABR-induced RP have been limited [13,17,18,28-30]. Barriger and others reported correlations between total lung MLD (<4 Gy vs. >4 Gy), lung V 20 (<4% vs. >4%) and grade 2–4 RP among patients treated with SABR to total doses of 42–60 Gy given in 8- to 20-Gy fractions [31].…”

Long-Term Outcomes of Salvage Stereotactic Ablative Radiotherapy for Isolated Lung Recurrence of Non–Small Cell Lung Cancer: A Phase II Clinical Trial

“…The internal gross target volume (IGTV) was contoured according to the maximal intensity projection. 15 Image-guided stereotactic body radiotherapy with a dose of 50 Gy in four fractions was prescribed to the planning target volume (PTV). For patients with local recurrence (in the field of previous radiotherapy), compromised PTV coverage or an alternative prescription dose is allowed to meet with normal tissue dose constraints.…”

Nondosimetric Risk Factors for Radiation-Induced Lung Toxicity

“…Recently, Liu et al analyzed 72 patients treated with stereotactic ablative radiation therapy (SABR) after previous thoracic RT and found 20.8% of patients developed grade ≥3 RP. ECOG PS scores of 2–3 before SABR, FEV1 ≤65% before SABR, V20≥30% of the composite plan, and an initial PTV in the bilateral mediastinum were significantly associated with increased risk of RP [65]. Therefore, previous thoracic RT is not a contraindication for RT when recurrent or secondary lung tumors occurred.…”