Table 2 Treatment planning and delivery characteristics

Patient position

 • Supine position with arms above the head

Immobilization device

 • Thermoplastic body mask

 • Styrofoam block for abdominal compression

CT scan

 • Contrast-free and 3 phases contrast-enhanced

 • Acquisition in free quiet breathing mode

 • 3-mm slice thickness

4-dimensional CT (4DCT)

 • In case of lesions located in the postero-superior segments, or with a shift greater than 5 mm on the CT scan

GTV delineation

 • CT scan

 • Co-registration with magnetic resonance imaging (MRI) or positron emission tomography (PET)

ITV and PTV delineation

 • For patients with 4D-CT, an internal target volume (ITV) was defined as the envelope of all GTVs in the different respiratory phases.

 • PTV = ITV + overall isotropic margin of 5 mm

 • PTV = GTV + 7–10 mm in the cranial-caudal axis and 4–6 mm in the anterior-posterior and lateral axes

Prescription dose

 • 75 Gy/ 3 fractions (Full dose)

 • 67.5 Gy/ 3 fractions (Reduction of 10%)

 • 60 Gy/ 3 fractions (Reduction of 20%)

 • 52.5 Gy/ 3 fractions (Reduction of 30%)

Dose constraints for OARs

 • Healthy liver: V15 Gy (volume receiving 15 Gy) < (total liver volume - 700 cm3)

 • Spinal cord: D 0.1 cm3 < 18 Gy

 • Both kidneys: V15 Gy < 35%

 • Duodenum, small bowel, esophagus, and stomach: V21 Gy < 1%

 • Heart: V30 Gy < 1%

 • Ribs: D30 cm3 < 30 Gy

 • dose fall off: from 100 to 30% in 5 mm

IGRT system

 • Megavoltage CBCT before each daily session