Author: Nrusingh C. Biswal, Sally Cheston, Sung-Woo Lee, Weiguang Yao, Baoshe Zhang 👨🔬
Affiliation: Department of Radiation Oncology, University of Maryland School of Medicine 🌍
Purpose: The deep inspiration breath-hold (DIBH) technique in left breast radiation reduces doses to critical organs such as the heart, left lung, and left anterior descending artery (LAD). With the adoption of an accelerated regimen is increasingly being adopted in clinics using volumetric modulated arc therapy (VMAT) as well as 3D conformal radiation therapy (3DCRT), using surface guided radiation therapy (SGRT). This study investigates the feasibility of converting VMAT or 3DCRT plans to free-breathing (FB) treatment if DIBH is interrupted.
Methods: A retrospective analysis of 14 treatment plans (3DCRT and VMAT) was conducted. Prescription doses ranged from 40.05 Gy (15 fractions) to 50 Gy (25 fractions), with 3 plans using 3DCRT and 11 using VMAT. Critical organ parameters included V10 and V20 for the left lung, Dmax, Dmean, V20, V40 for the heart, and maximum and mean doses for the heart and LAD. DIBH treatments utilized SGRT.
Results: DIBH plans consistently reduced doses to critical organs compared to FB plans. However, reductions in left lung dose were not consistently observed for either 3DCRT or VMAT. 3DCRT DIBH plans showed greater reductions in heart and LAD doses compared to VMAT. For instance, maximum and average heart doses decreased by 84.03% and 63.64% for 3DCRT DIBH plans, versus 26.06% and 18.97% for VMAT. Statistical analysis (P = 0.00000104) showed significantly better performance of 3DCRT over VMAT for DIBH vs. FB plans.
Conclusion: In cases where DIBH is unavailable, FB can be used as a backup. However, 3DCRT is more sensitive to deviations from the original DIBH plan than VMAT. The dose reduction with VMAT from FB to DIBH is less significant than with 3DCRT. Thus, when 3DCRT DIBH is interrupted, it is better to wait for DIBH to be reinstated, while VMAT can continue with FB.