S2719
RTT - Patient preparation, immobilisation, and verification protocols
ESTRO 2026
1871 Implementation of deep inspiration breath-hold technique in lung SBRT: feasibility, accuracy and tolerance jihad aslaoui 1 , Nicolas Wagneur 1 , Josué Ezechiel Josias BIAOU 1 , Damien Autret 2 , Quentin Josset 1 , Amaury Paumier 1 1 Radiotherapy, Institut de cancérologie de l'Ouest, Angers, France. 2 medical physics, Institut de cancérologie de l'Ouest, Angers, France Purpose/Objective: Stereotactic body radiotherapy (SBRT) has become a standard treatment for early stage or oligometastatic lung tumors. However, respiratory motion remains a major challenge affecting targeting accuracy. While the Deep Inspiration Breath-Hold (DIBH) technique is routinely used in breast radiotherapy to reduce cardiac and pulmonary doses, its application in lung SBRT remains limited. Our study aimed to evaluate the feasibility, patient tolerance, and reproducibility intra- and inter-fraction of a DIBH-based lung SBRT protocol at our institution. Material/Methods: We conducted a retrospective descriptive monocentric study in our department, including eleven patients treated with lung SBRT in DIBH conditions. Each patient underwent comparative 4DCT and DIBH scans according to the institutional protocol (Figure 1). Planning target volumes (PTVs) generated with the internal target volume (ITV) approach were compared with those obtained in DIBH. Dice similarity index and tumor centroid displacements between successive DIBH acquisitions [Day 1 (D1), Day 2 Version 1(D2V2), Day 2 Version 2 (D2V2)] were analyzed. Image guidance and verification procedures were performed following a predefined imaging protocol (Figure 2). We also conducted a dosimetric evaluation and assessed the treatment delivery parameters across 49 sessions (93 arcs). This included session duration, the number and length of breath-holds, setup deviations, and patient tolerance. Differences between PTV volumes were analyzed using the Wilcoxon test implemented via an in-house Python script.
Results: Median age was 72 years, with 81.8% male patients and predominantly primary lesions (81.8%), mainly in lower lobes. DIBH planning significantly reduced PTVs compared to ITV-based planning (p = 0.0002). Median Dice coefficients ranged from 0.60 to 0.77, and median centroid displacements between repeated DIBH scans were 2.3–3.1 mm, confirming good reproducibility. Dosimetric objectives were achieved in all but one case, with all organ-at-risk constraints respected. Median treatment time was 17 minutes, with a mean of two breath-holds per arc (mean duration 51 seconds). Intra- and inter-fraction positioning deviations remained below 5 mm, except for one patient requiring replanning. Overall tolerance was excellent, with only minor transient events (cough, mild rib pain). Conclusion: This first institutional experience demonstrates that lung SBRT under DIBH is both feasible and reproducible, providing significant target volume reduction while maintaining excellent patient tolerance. These encouraging results support broader implementation of DIBH in lung SBRT, potentially
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