Correlation of Clinical and Dosimetric Parameters With Radiographic Lung Injury Following Stereotactic Body Radiotherapy

Abstract

Radiographic changes occur in over half of patients treated with stereotactic body radiotherapy (SBRT) to the lung, correlating histopathologically with injury. We quantified radiographic density changes (ie, fibrosis) at 3, 6, and 12 months and investigated the relationship between these volumes and clinical and dosimetric parameters. The study population consisted of patients treated with SBRT to the lung for stage I primary lung cancers (n = 39) or oligometastatic lesions (n = 17). Fractionation schemes included 3 fractions of 12, 14, or 18 gray (Gy) and 4 fractions of 12 or 12.5 Gy prescribed to cover 95% of the planning target volume (PTV). Planning computed tomography (CT) scans were rigidly registered to follow-up CT scans obtained at intervals of 3, 6, and 12 months. Fibrotic volumes were contoured on the follow-up scans. Associations between the volume of fibrosis and clinical and dosimetric parameters were investigated using univariate linear regression. Scans were available for 65 and 47 lesions at 6 and 12 months, respectively. Age, years since quitting smoking, and GOLD Global Initiative for Chronic Obstructive Lung Disease score were significantly associated with increasing volume of fibrosis (P < .05). Total dose, dose per fraction, PTV, and volumetric parameters (V0-V55) were also significantly associated with increasing volumes of fibrosis (P < .01). For dosimetric parameters, the effect was largest for V55. Age, significant smoking history, and GOLD score were significantly associated with increasing volumes of fibrosis following SBRT. In a multivariate model adjusted for age and smoking history, V10 through V50 and PTV size remained significant predictors of fibrotic volume. Further, there is a strong dose-response relationship between the volume of lung exposed to a certain dose and the fibrotic volume. The predominant kinetic patterns of fibrosis demonstrate peaking fibrotic volumes at 6 and 12 months. These results provide insight for expectations of fibrosis after SBRT.

Comprehensive dosimetric planning comparison for early‐stage, non‐small cell lung cancer with SABR: fixed‐beam IMRT versus VMAT versus TomoTherapy

“…The maximum point dose () to nearby critical organs at risk (OAR), such as the esophagus, spinal cord, heart, trachea, and proximal bronchus was compared amongst all patients. Lung toxicity parameters analyzed include the absolute volume of normal lung covered by 50% of the prescription or more (), predictive of fibrosis, (23) the mean dose to the normal lung (MLD), the normal lung receiving 5, 10, 20, 27 Gy or more (, respectively), and contralateral lung receiving at least 5 or 10 Gy (, respectively).…”

Lung density change after SABR: A comparative study between tri-Co-60 magnetic resonance-guided system and linear accelerator

“…Patient-related factors such as age, smoking history, tumor size, tumor location, performance score, and gender- and treatment-related factors including chemotherapy regimen and lung dosimetry have been suggested as predictors for the development of RILD [ 25 – 27 ]. In regards to radiographic change, Kishan et al [ 28 ] reported that age, years since quitting smoking, and GOLD (Global Initiative for Chronic Obstructive Lung Disease) score were significantly associated with volumes of radiographic fibrosis following SABR. They found the predominant patterns of fibrosis peaking volumes of fibrosis at 6 and 12 months.…”

Radiation Therapy for Stage I Nonoperable or Medically Inoperable Lung Cancer

“…78 Because most cases of radiation fibrosis involve patchy consolidation or ground-glass densities that develop at 3 months posttreatment and continue to evolve over time, reliance on CT alone may be insufficient in discriminating between fibrosis and recurrence. [79][80][81][82] Takeda et al queried follow-up imaging from 50 patients treated with SBRT who had at least 12 months of follow-up imaging, with a median follow-up of 30.4 months. 83 They noted suspicious opacities in 20 patients (40%); only 3 (6%) actually had proven recurrences, and 14 (70% of those with suspicious opacities) did not.…”

“…82,[85][86][87][88][89][90] Kishan et al recently quantified fibrotic changes at 3, 6, and 12 months in 56 patients treated with SBRT. 82 The predominant kinetic patterns of fibrosis demonstrated peaking fibrotic volumes at 6 and 12 months, and the investigators found that age, years since quitting smoking, and Global Initiative for Chronic Obstructive Lung Disease score were significantly associated with increasing volume of fibrosis. The investigators also found that a variety of dosimetric parameters were associated with increasing volumes of fibrosis.…”