Lung Cancer

PD 18 - Lung 5 - Poster Discussion - SBRT

1159 - Breathing-Motion-Compensated Stereotactic Body Radiation Therapy for Moving Targets of the Lung: A Patterns of Failure Analysis

Wednesday, October 24
2:06 PM - 2:12 PM
Location: Room 217 C/D

Breathing-Motion-Compensated Stereotactic Body Radiation Therapy for Moving Targets of the Lung: A Patterns of Failure Analysis
Y. S. Butler-Xu1, S. S. Sood1, W. Yap2, M. J. Tennapel1, H. Jiang1, R. K. Badkul1, A. M. Chen1, and F. Wang1; 1Department of Radiation Oncology, University of Kansas School of Medicine, Kansas City, KS, 2Department of Radiology, University of Kansas School of Medicine, Kansas City, KS

Purpose/Objective(s): The influence of tumor motion on dose delivery in stereotactic body radiation therapy (SBRT) for lung cancer using 3-D arc therapy, fixed field intensity modulated radiation therapy, and volumetric modulated arc therapy has been studied, but its clinical impact has not been well defined. We retrospectively evaluated the patterns of failure for breathing-motion-compensated stereotactic body radiation therapy (SBRT) in the treatment of lung cancers.

Materials/Methods: Between May 2009 and July 2016, a total of 106 patients with early stage non-small cell carcinoma of the lung (NSCLC) were treated with breathing-motion-compensated SBRT. Patients were simulated with free-breathing 4-dimensional computed tomography (4-DCT) to generate internal target volume (ITV) for breathing motion compensation. The median gross tumor volume (GTV) and ITV were 7.1 cc (0.55 – 192 cc) and 7.6 cc (0.55 – 206 cc), respectively. Median biologically effective dose (BED; α/β = 10 Gy) prescribed to the planning target volume was 100 Gy (100 – 151 Gy). We analyzed local control, regional control, nodal control, freedom from metastasis, overall survival, and lung cancer specific survival based on target motion volume (calculated by subtracting GTV from ITV) as well as dosimetric parameters (BED, GTV, and ITV) and patient characteristics (age, history of other malignancies, tumor histology, T stage, lobe location, and PET scan parameters).

Results: Median follow up was 22 months (1- 95 months). The 2 year rates of local control, regional control, nodal control, and freedom from metastasis were 93%, 94%, 77%, and 81%, respectively. Overall survival and lung cancer specific survival at 2 years were 81% and 96%, respectively. Median target motion volume was 0.8cc (0 – 16cc). Target motion volume was larger for tumors in the lower lobes (p=0.01) as well as tumors with larger GTV (p<0.0001). On univariate analysis, we found that higher target motion volume was a significant predictor for decreased local control (p=0.0013), nodal control (p=0.0089), freedom of metastasis (p=0.0003), and overall survival (p=0.0091). There was no correlation between target motion volume and incidence of pneumonitis (p=0.4) or rib fracture (p=0.5). Other factors examined were not predictors for clinical outcome except for T stage (T1a predicted for higher local control (p=0.0078)) and PET volume (higher tumor volume on PET was associated with decreased nodal control (p=0.0075) and lung cancer specific survival (p=0.027)).

Conclusion: Our study demonstrates that target motion volume is a significant predictor for clinical outcome in patients with early stage NSCLC treated with breathing-motion-compensated SBRT. To our knowledge this is the first study to exhibit the potential clinical impact of target motion in NSCLC patients treated with SBRT. Further studies from the perspectives of physics and radiation biology are warranted.

Author Disclosure: Y.S. Butler-Xu: None. S.S. Sood: None. W. Yap: None. M.J. Tennapel: None. H. Jiang: None. R.K. Badkul: None. F. Wang: None.

Yiqing Butler-Xu, MD

Disclosure:
Employment
University of Kansas: Resident Physician: Employee

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