Local Control and Toxicity in a Large Cohort of Central Lung Tumors Treated With Stereotactic Body Radiation Therapy

Abstract

Purpose/Objective(s) Stereotactic body radiotherapy (SBRT) in central lung tumors has been associated with higher rates of severe toxicity. We sought to evaluate toxicity and local control in a large cohort, and to identify predictive dosimetric parameters. Methods and Materials We identified patients who received SBRT for central tumors according to either of two definitions. Local failure (LF) was estimated using a competing-risks model, and multivariate analysis (MVA) was used to assess factors associated with LF. We reviewed patient toxicity, and applied Cox proportional hazard analysis and logrank tests to assess whether dose-volume metrics of normal structures correlated with pulmonary toxicity. Results One hundred twenty-five patients received SBRT for NSCLC (n=103) or metastatic (n=22) lesions using IMRT. The most common dose was 45Gy in 5 fractions. Median followup was 17.4 months. Incidence of grade ≥ 3 toxicity was 8.0%, including 5.6% pulmonary toxicity. Sixteen patients (12.8%) experienced grade ≥2 esophageal toxicity, including 50% of patients where PTV overlapped the esophagus. There were two treatment-related deaths. Among patients receiving biologically effective dose (BED) ≥ 80 Gy (n=108), 2-year LF was 21%. On MVA, gross tumor volume (GTV) was significantly associated with LF. None of the studied dose-volume metrics of the lungs, heart, proximal bronchial tree (PBT), or 2 cm expansion of the PBT (“no-fly-zone” or NFZ) correlated with grade ≥ 2 pulmonary toxicity. There was no difference in pulmonary toxicity between central tumors located inside the NFZ, and those outside the NFZ but with planning target volume (PTV) intersecting the mediastinum. Conclusion Using moderate doses, SBRT for central lung tumors achieves acceptable local control with low rates of severe toxicity. Dosimetric analysis showed no significant correlation between dose to the lungs, heart, or NFZ and severe pulmonary toxicity. Esophageal toxicity may be an underappreciated risk, particularly when PTV overlaps the esophagus.

Textural features in pre-treatment [F18]-FDG-PET/CT are correlated with risk of local recurrence and disease-specific survival in early stage NSCLC patients receiving primary stereotactic radiation therapy

“…Additionally, in our study, tumor size alone was predictive for local failure; LR occurred solely in tumors measuring more than 3 cm. This association has been reported in earlier studies as well [21,26] and should be kept in mind as possibly undermining the correct interpretation of data on local failure in SBRT, perhaps originating from insufficient and/or inhomogeneous dose delivery to larger tumors [27]. However, when only tumors larger than 3 cm were examined (i. e. T2 tumors), texture as measured by the features entropy and correlation, but not MTV or tumor size in CT, were significantly correlated with LR.…”

Optimizing the flattening filter free beam selection in RapidArc®-based stereotactic body radiotherapy for Stage I lung cancer

“…Treating central lung tumours with SBRT has been reported to induce oesophageal toxicities. Modh et al 36 reported that 12.8% patients with central lung tumour experienced $ grade 2 oesophageal toxicity after SBRT treatment. Wu et al 37 found that the incidence of grade $2 acute toxicity was 12%.…”

LungTech, an EORTC Phase II trial of stereotactic body radiotherapy for centrally located lung tumours: a clinical perspective

“…9,36,[50][51][52][53]56,57,[59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75] In terms of tumour dose, the LungTech protocol will investigate a medium hypofractionated approach, applying 8.0 3 7.5 Gy to a total dose of 60 Gy; this is equal to a BED of 105 Gy (a/b 5 10). Referring to report 83 of the International Commission on Radiation Units and Measurements (ICRU), 95% of the PTV has to receive at least the nominal fraction dose, and 99% of the PTV receives a minimum of 90% of the nominal dose.…”