Analysis of Lung Tumor Motion in a Large Sample: Patterns and Factors Influencing Precise ITV Delineation

Publication date: Available online 20 August 2016
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Lukas Knybel, Jakub Cvek, Lukas Molenda, Natalie Stieberova, David Feltl
Purpose/Objective: To evaluate lung tumor motion during respiration and describe factors affecting the range and variability of motion in patients treated with stereotactic ablative radiotherapy.MethodsLog file analysis from online respiratory tumor tracking was performed in 145 patients. Geometrical tumor location in the lungs, tumor volume and origin (primary or metastatic), gender, and tumor motion amplitudes in the superior-inferior (SI), latero-lateral (LL), and anterior-posterior (AP) directions were recorded. Tumor motion variability during treatment was described using intra/interfraction amplitude variability and tumor motion baseline changes. Tumor movement dependent on the tumor volume, position, and origin and gender were evaluated using statistical regression and correlation analysis.ResultsAfter analyzing >500 hours of data, the highest rates of motion amplitudes, intra/interfraction variation, and tumor baseline changes were in the SI direction (6.0±2.2 mm, 2.2±1.8 mm, 1.1±0.9 mm, and −0.1±2.6 mm). Mean motion amplitudes in the lower/upper geometrical halves of the lungs were significantly different (p<0.001). Motion amplitude >15 mm was observed only in the lower geometrical quarter of the lungs. Higher tumor motion amplitude generated higher intrafraction variation (R=0.86, p<0.001). Interfraction variation and baseline change >3 mm indicated tumors contacting mediastinal structures or parietal pleura. On univariate analysis, neither gender nor tumor origin (primary vs. metastatic) were independent predictive factors of different movement patterns. Metastatic lesions in women, but not men, showed significantly higher mean amplitudes (p=0.03) and variability (primary, 2.7 mm; metastatic, 4.9 mm; p=0.002) than primary tumors.ConclusionOnline tracking showed significant irregularities in lung tumor movement during respiration. Motion amplitude was significantly lower in upper lobe tumors; higher interfraction amplitude variability indicated tumors in contact with mediastinal structures, though adhesion to parietal pleura did not necessarily reduce tumor motion amplitudes. The most variable lung tumors were metastatic lesions in women.

Teaser

Understanding patterns of tumor motion and involving them in treatment planning is important for performing precise lung radiotherapy. Data from online tumor tracking was used to evaluate respiratory motions of lung tumors and describe factors affecting range of motion and motion variability during radiotherapy.


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