2023 World Conference on Lung Cancer (Posters)-EP08.02. Optimal Planning Target Volume Margins for Spirometer-Based DIBH Radiotherapy for Lung Cancer

EP08.02. Optimal Planning Target Volume Margins for Spirometer-Based DIBH Radiotherapy for Lung Cancer - PDF(Slides)

Pdf Summary

This study aimed to estimate lobe-specific margins for the planning target volume (PTV) in spirometer-based deep-inspiration breath-hold (DIBH) radiotherapy for lung cancer. Ten patients with locally advanced or recurrent non-small cell lung cancer (NSCLC) were enrolled in this prospective study. CT scans were performed using spirometer-based DIBH, and twelve bronchial bifurcation points were manually defined. The systematic and random errors of the bifurcation positions were estimated. Based on previous reports, PTV margins were calculated using the van Herk formula. <br /><br />The estimated PTV margins varied depending on the matching scenario. In the vertebral body matching scenario, the margins ranged from 0.1 to 3.0 mm, 0.3 to 4.3 mm, and 0.2 to 4.6 mm in the right-left, anterior-posterior, and superior-inferior directions, respectively. In the carina matching scenario, the margins ranged from 0.0 to 2.7 mm, 0.1 to 3.6 mm, and 0.0 to 5.2 mm in the right-left, anterior-posterior, and superior-inferior directions, respectively. The PTV margin for the carina matching scenario was 5 mm, except for the Ltri bronchial bifurcation point in the superior-inferior direction.<br /><br />The reproducibility of the spirometer-based DIBH technique was considered acceptable in both matching scenarios. However, for tumors located in the Ltri bronchial bifurcation point, a larger PTV margin of 5 mm in the superior-inferior direction was required. <br /><br />Overall, these findings provide guidance on lobe-specific margins for the planning target volume in spirometer-based DIBH radiotherapy for lung cancer, which can contribute to the reduction of the irradiated lung volume and the risk of radiation pneumonitis. However, limitations of the study include not considering tumor shrinkage over time, inter-fractional rotational error, and prior history of pulmonary resection.

Asset Subtitle

Noriko Kishi

Meta Tag

Speaker Noriko Kishi

Topic Local-Regional NSCLC: Multimodality Therapy

Keywords

lobe-specific margins

planning target volume

PTV

spirometer-based DIBH

radiotherapy

lung cancer

NSCLC

bronchial bifurcation points

reproducibility

irradiated lung volume