An evaluation of planning techniques for stereotactic body radiation therapy in lung tumors

Abstract

Purpose To evaluate four planning techniques for stereotactic body radiation therapy (SBRT) in lung tumors. Methods and materials Four SBRT plans were performed for 12 patients with stage I/II non-small-cell lung cancer under the following conditions: (1) conventional margins on free-breathing CT (plan 1), (2) generation of an internal target volume (ITV) using 4DCT with beam delivery under free-breathing conditions (plan 2), (3) gating at end-exhale (plan 3), and (4) gating at end-inhale (plan 4). Planning was performed following the RTOG 0236 protocol with a prescription dose of 54 Gy (3 fractions). For each plan 4D dose was calculated using deformable-image registration. Results There was no significant difference in tumor dose delivered by the 4 plans. However, compared with plan 1, plans 2–4 reduced total lung BED by 1.9 ± 1.2, 3.1 ± 1.6 and 3.5 ± 2.1 Gy, reduced mean lung dose by 0.8 ± 0.5, 1.5 ± 0.8, and 1.6 ± 1.0 Gy, reduced V20 by 1.5 ± 1.0%, 2.7 ± 1.4%, and 2.8 ± 1.8%, respectively, with p < 0.01. Compared with plan 2, plans 3–4 reduced lung BED by 1.2 ± 1.0 and 1.6 ± 1.5 Gy, reduced mean lung dose by 0.6 ± 0.5 and 0.8 ± 0.7 Gy, reduced V20 by 1.2 ± 1.1% and 1.3 ± 1.5%, respectively, with p < 0.01. The differences in lung BED, mean dose and V20 of plan 4 compared with plan 3 were insignificant. Conclusions Tumor dose coverage was statistically insignificant between all plans. However, compared with plan 1, plans 2–4 significantly reduced lung doses. Compared with plan 2, plan 3–4 also reduced lung toxicity. The difference in lung doses between plan 3 and plan 4 was not significant.