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

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.