Alternating expiration and inspiration breath-hold spares the chest wall during stereotactic body radiotherapy for peripheral lung malignancies.

PURPOSE: The proximity of tumors to the chest wall brings additional risks of chest wall pain during stereotactic body radiotherapy (SBRT). Herein, we dosimetrically compared alternated breath-hold (ABH) plans with single BH plans, as well as to determine the common characteristics of eligible patients who may obtain better chest wall sparing using this technique.

METHODS AND MATERIALS: Twenty patients with lung lesions adjacent to the chest wall were enrolled and received respiratory training. Their half-fractions end-expiration (EEBH) and deep inspiration breath-hold (DIBH) plans were summed to generate the ABH plans. Dosimetric parameters of the chest wall were compared between single and alternated BH plans. And the correlation between tumor location and the outcome of chest wall sparing was quantitatively evaluated. Pre-treatment CBCT variations in eligible patients were recorded as well.

RESULTS: Compared to the EEBH and DIBH plans, the ABH plans reduced chest wall dosimetric results with median reductions of 2.0% and 3.9% (Dmax), 15.4% and 14.8% (D1cc), 48.8% and 63% (V30), respectively. Relative tumor displacements (SI/d value) were greater in the lower lobe than in the upper and middle lobes (1.17 vs. 0.18). Meanwhile, better median reductions of 44% (Dmax), 46% (D1cc), and 98% (V30) were obtained in the lower lobe cohort using the ABH technique. Pre-treatment variations for all BHs met the 5 mm threshold.

CONCLUSIONS: The ABH technique can significantly spare the adjacent chest wall without compromising PTV coverage in comparison with the single BH. And patients with tumors in the lower lobes can obtain better chest wall sparing than in the upper and middle lobes. Further investigation is warranted to validate these findings.