Original Articles
Radiological Changes After Stereotactic Radiotherapy for Stage I Lung Cancer

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Introduction

Stereotactic body radiation therapy (SBRT) is entering routine clinical use for selected patients with early-stage non-small cell lung cancer. Post-SBRT radiological changes are commonly seen on follow-up computed tomography (CT) imaging and can cause diagnostic dilemmas. The aim of this study is to describe the incidence, radiological severity, and long-term morphology of these changes.

Methods

CT scans from patients treated between 2003 and June 2008 were eligible for evaluation if radiological follow-up had been performed at our center for at least 2 years, and there was no definite evidence of local recurrence. Timing, incidence, morphology, and severity of lung changes were determined.

Results

CT scans from 61 patients (68 lesions) with a median follow-up of 2.5 years were evaluated. Within 6 months, 54% of lesions were associated with additional radiological abnormalities, and this figure reached 99% after 36 months. Most changes were scored as mild to moderate, and although the median time to first observation was 17 weeks, 25% appeared ≥1 year post-SBRT. In 47% of lesions, the morphology or severity of changes continued to evolve more than 2 years posttreatment.

Conclusions

Mild-moderate radiological changes are common after lung SBRT. Some degree of late change is nearly universal, and it often continues to evolve more than 2 years post-SBRT. Clinicians should be aware of these radiological findings, which need to be distinguished from the uncommon cases of local failure post-SBRT.

Key Words

Lung cancer
Radiation fibrosis
Radiation pneumonitis
Radiation therapy
Stereotactic

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Disclosure: VU University Medical Center has research collaborations with Varian Medical Systems, Palo Alto, CA, BrainLAB AG, Feldkirchen, Germany, and Velocity Medical Solutions, Atlanta, GA. Max Dahele, MBChB, has received travel support from Varian Medical Systems and BrainLAB; Frank Lagerwaard, MD, PhD, has received honoraria from Varian Medical Systems; Ben Slotman, MD, PhD, has received speaker's fees from Varian Medical Systems and BrainLAB; and Suresh Senan, FRCR, PhD, has received speaker's fees from Varian Medical Systems.

The first two authors contributed equally to this work.