Volumetric Arc Therapy Seems More Promising for Sparing Organs at Risk in Adjuvant Postoperative Radiotherapy for Pancreatic Adenocarcinoma than Step-and-Shoot Intensity-Modulated Radiotherapy
Yasemin BÖLÜKBAŞI1,Yücel SAĞLAM2,Duygu SEZEN1,Z. Vildan ALPAN2,Steve KIRSNER3,Uğur SELEK1
1Department of Radiation Oncology, Koç University Faculty of Medicine, Istanbul-Turkey
2Department of Radiation Oncology, American Hospital-MD Anderson Radiation Treatment Center, İstanbul-Turkey
3Department of Radiation Oncology, MD Anderson Cancer Center, Houston-USA
DOI : 10.5505/tjo.2017.1588 OBJECTIVE
The aim of the present study was to determine if volumetric modulated arc therapy (VMAT) provided superior dose distribution than intensity-modulated radiotherapy (step-and-shoot; ssIMRT) based on target volume coverage and organs at risk (OARs) doses in postoperative radiotherapy for pancreatic cancer patients.

New 4-dimensional computed tomography plans for 10 pancreatic cancer patients were created. The ssIMRT plans had 6 coplanar fields (330-0-30-60-90°) and VMAT plans were generated with 2 268-92° arcs.

VMAT plans revealed better overall sparing of right kidney (volume receiving 15% of prescribed dose [V15]: 28.3% vs 46.9%, p=0.012; V20: 16.1% vs 27.6%, p=0.007; V25: 8.6% vs 15.2%, p=0.005; mean dose 1549 centigray [cGy] vs 1987 cGy, p=0.005). VMAT delivered similar isodose distribution (planning target volume [PTV] mean dose: 5164 vs 5183 cGy, PTV max: 5526 cGy vs 5505 cGy; p=0.541) with significantly fewer monitor units (MU) (MU: 468 vs 527; p=0.032) in comparison with ssIMRT. VMAT was also found to be superior for V30 intestinal dose, but mean dose was similar (1963 cGy vs 2032 cGy; p=0.05).

VMAT provided more effective protection for bilateral kidneys and small intestine with better OAR doses, as well as for liver, with reduced high-dose volumes in this cohort. This could be investigated as more tolerable concurrent radiochemotherapy treatment with better OAR preservation. Keywords : Intensity-modulated radiation therapy; pancreatic cancer; volumetric modulated arc therapy