Optimal planning strategy among various arc arrangements for prostate stereotactic body radiotherapy with volumetric modulated arc therapy technique

The aim of this study was to determine the optimal strategy among various arc arrangements in prostate plans of stereotactic body radiotherapy with volumetric modulated arc therapy (SBRT-VMAT).

To investigate how arc arrangements affect dosimetric and biological metrics, SBRT-VMAT plans for eighteen patients were generated with arrangements of single-full arc (1FA), single-partial arc (1PA), double-full arc (2FA), and double-partial arc (2PA). All plans were calculated by the Acuros XB calculation algorithm. Dosimetric and radiobiological metrics for target volumes and organs at risk (OARs) were evaluated from dosevolume histograms.

All plans were highly conformal (CI<1.05, CN=0.91) and homogeneous (HI=0.09-0.12) for target volumes. For OARs, there was no difference in the bladder dose, while there was a significant difference in the rectum and both femoral head doses. Plans using 1PA and 2PA showed a strong reduction to the mean rectum dose compared to plans using 1FA and 2FA. Contrastively, the D2% and mean dose in both femoral heads were always lower in plans using 1FA and 2FA. The average tumor control probability and normal tissue complication probability were comparable in plans using all arc arrangements.

The use of 1PA had a more effective delivery time and produced equivalent target coverage with better rectal sparing, although all plans using four arc arrangements showed generally similar for dosimetric and biological metrics. However, the D2% and mean dose in femoral heads increased slightly and remained within the tolerance. Therefore, this study suggests that the use of 1PA is an attractive choice for delivering prostate SBRT-VMAT.

Radiology and oncology. 2017 Jan 15*** epublish ***

Sang Won Kang, Jin Beom Chung, Jae Sung Kim, In Ah Kim, Keun Yong Eom, Changhoon Song, Jeong Woo Lee, Jin Young Kim, Tae Suk Suh

Research Institute of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seoul, Korea; Department of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seoul, Korea., Department of Radiation Oncology, Seoul National University Bundang Hospital, Seongnam, Korea., Department of Radiation Oncology, Konkuk University Medical center, Seoul, Korea., Department of Radiation Oncology, Haeundae Paik Hospital, Inje University, Busan, Korea.