Stereotactic radiotherapy for peripheral lung tumors: a comparison of volumetric modulated arc therapy with 3 other delivery techniques.

PURPOSE: Volumetric modulated arc therapy (RapidArc) allows for fast delivery of stereotactic body radiotherapy (SBRT) delivery in stage I lung tumors. We compared dose distributions and delivery times between RapidArc and common delivery techniques in small tumors. METHODS: In 18 patients who completed RapidArc SBRT for tumors measuring <70 cm(3), new treatment plans were generated using non-coplanar 3D conformal fields (conf-SBRT) and dynamic conformal arc radiotherapy (DCA). For 9 patients with tumors adjacent to the chest wall, co-planar intensity-modulated radiotherapy (IMRT) plans were also generated. PTV dose coverage, organs at risk (OAR) doses and treatment delivery times were assessed. RESULTS: RapidArc plans achieved a superior conformity index (CI) and lower V(45 Gy) to chest wall (p<0.05) compared to all other techniques. RapidArc led to a small increase in V(5 Gy) to contralateral lung compared to conf-SBRT (4.4±4% versus 1.2±1.8%, p=0.011). For other OAR, RapidArc and conf-SBRT plans were comparable, and both were superior to DCA plans. Delivery of a 7.5 Gy-fraction required 3.9 min (RapidArc), 11.6 min (conf-SBRT), and 12 min (IMRT). CONCLUSIONS: In stage I lung tumors measuring <70 cm(3), RapidArc plans achieved both the highest dose conformity and shortest delivery times.