Objective: This retrospective study constitutes a feasibility assessment of dynamic conformal arc (DCA) therapy as an alternative to volumetric-modulated arc therapy (VMAT) for stereotactic body radiation therapy (SBRT) of lung cancer (LC) with the free breathing technique using internal target volume. DCA is to create a more efficient treatment reducing beam-on time (BOT) and monitor unit (MU) without interplay errors except for complex tumor geometries when compared to volumetric modulated arc therapy (VMAT).
Materials and Methods: CT images and plans of forty patients treated with 50 Gy prescription in four fractions using VMAT technique for SBRT treatment of LC selected. Plans were re-planned with using DCA technique. VMAT and DCA plans compared via The Radiation Therapy Oncology Group (RTOG) Protocol 0915 for conformity and efficient having pass rate of gamma index in quality assurance (QA), MU and BOT.
Results: The study included 40 patients. The mean value of QA pass rate 99.10±1.49 in DCA and 92.34±1.96 in VMAT. The rate was higher in DCA (p<0.001 and t=8.98). The values of BOT and MU were 4.68 min and 3296 in the VMAT technique and they were 3.58 min and 2395 in DCA. These values were significantly improved with DCA (p<0.001 and p<0.001).
Conclusion: DCA can potentially minimize multi-leaf collimator errors from respiratory motion and small-field dosimetry. It delivery similar doses of treatment quality to tumor while providing faster treatment by significantly reducing MU and BOT compared to VMAT and moreover offers sameday SBRT treatments without the need for specific QA.