A novel modified dynamic conformal arc technique for treatment of peripheral lung tumors using stereotactic body radiation therapy.

Purpose: To describe and compare a novel, modified dynamic conformal arc (MDCA) technique for lung stereotactic body radiation therapy with the standard noncoplanar beam (NCB) technique based on stereotactic body radiation therapy (SBRT) coverage, dose conformality, normal tissue constraints, and treatment time.

Materials And Methods: Twenty consecutive medically inoperable patients with early stage, peripheral, non-small cell lung cancer treated with SBRT using an NCB technique were re-planned with a novel MDCA technique. Treatment plans were compared based on Radiation Therapy Oncology Group (RTOG) 0236 criteria for planning treatment volume (PTV) coverage and normal tissue dose constraints, as well as high- and moderate-dose conformality. Treatment times necessary to deliver the NCB plans were compared with the times of a separate group of 12 consecutive patients treated with the MDCA technique at our institution.

Results: The MDCA technique resulted in improved coverage of the cranial and caudal regions of the PTV and generated plans that were significantly more conformal by all high-dose criteria proposed by the RTOG protocol. In terms of moderate-dose criteria, MDCA plans had a significantly lower maximum dose (2 cm from the PTV), whereas the ratio of the 50% dose volume to the volume of the PTV was equivalent between the 2 techniques. All normal tissue dose constraints proposed in the RTOG 0236 protocol were met by each plan, although the median lung V20 and mean lung dose were slightly higher in the MDCA plans, whereas the chest wall dose was slightly lower. A 42% reduction in treatment time was observed when patients treated with the NCB technique were compared with a separate cohort of 12 patients treated with the MDCA technique (P < .0001).

Conclusions: The new MDCA technique described in this study resulted in enhanced PTV coverage, improved high- and moderate-dose conformality, simplified treatment planning, and reduced treatment time compared with results using the standard NCB technique.