Evaluation of the dynamic conformal arc therapy in comparison to intensity-modulated radiation therapy in prostate, brain, head-and-neck and spine tumors

To evaluate dynamic conformal arc therapy (DAT) dose distribution and clinical applicability in comparison to intensity-modulated radiotherapy (IMRT) in different types of tumors and locations, twelve patients with prostate cancer with no node involvement and three patients with single tumors in the pituitary, in the neck and in the thoracic spinal region treated with IMRT, were retrospectively planned with DAT using Eclipse (V8.1). The prostate cases were also planned with three-dimensional conformal radiation therapy (3DCRT). Dose distributions were evaluated through comparisons of dose-volumetric histograms and in-house IMRT protocol constraints, as well as validated via ion chamber array measurements. DAT plans for prostate showed a statistically comparable achievement of tumor conformity and dose sparing for bladder and rectum when compared to IMRT. Dose on femoral heads were similar to those achieved using 3DCRT. DAT could be planned with similar results to those obtained in IMRT for the dose constraints of the defined structures by using a 360 arc for the brain lesion and several arcs including noncoplanar ones for the head-and-neck and spinal tumors. Experimental validation of the calculated dose distributions via gamma analysis of composite distributions for DAT provided that more than 95% of the pixels satisfy the criteria 3 mm-3%, which was similar to that of IMRT. The average number of monitor units was approximately five times lower than IMRT. In conclusion, DAT is capable of providing conformal dose distributions to the targets accomplishing many of the IMRT dose constraints simultaneously. Experimental dose-validation accuracy, ease of planning and reduced treatment times make DAT both acceptable and attractive for clinical use.