Radiotherapy is very infrequently used in the setting of hepatocellular carcinoma. With the advent of stereotactic and image guided radiotherapy, it may become more common especially when patients are medically unfit for resection.
Palliative Radiotherapy
Treat the patient palliatively using 3D conformal radiotherapy, delivering a dose of 21 Gy in 7 fractions to the entire liver.
Pre-Simulation
Obtain informed consent.
Obtain functional renal imaging.
Simulation
Positioning
Patient lies supine
Immobilisation
Arms raised above head on wing board. Knee immobilisation with kneefix.
Image Acquisition
3 mm CT slices from carina to acetabulum.
Planning
Volumes
CTV = Entire liver
ITV = 1 cm sup and inf expansion
PTV = 1 cm further expansion
Organs at Risk
Liver < 30 Gy
Kidneys < 18 Gy mean, or L) kidney < 6 Gy if mean dose to R) Kidney > 18 Gy.
Small bowel < 40 Gy to 195 cc volume
Stomach < 55 Gy
Spinal Cord < 40 Gy
3D Conformal Technique
Treat the patient with radical radiotherapy using
Pre-Simulation
Ensure liver function has been assessed.
Obtain informed consent.
Simulation
Positioning
Patient lies supine.
Immobilisation
Arms elevated above head on wing board.
Kneefix.
Image Acquisition
CT scan with contrast from carina to acetabulum.
Consider 4D CT or fluoroscopy to evaluate tumour movement.
Planning
Volumes
GTV = Enhancing tumour as seen on CT
CTV = GTV + 1 cm (surgical series)
ITV = Extent of tumour motion as assessed on fluoroscopy or 4DCT (between 0.5 to 2.5 cm)
PTV = Further 0.7 cm expansion for daily setup variation.
Organs at Risk
Liver < 32 Gy mean dose
Kidney < 18 Gy mean dose, or if one kidney exceeds 18 Gy then the other kidney < 6 Gy mean dose
Small bowel < 45 Gy to 195 cc volume
Stomach < 55 Gy
Spinal cord < 45 Gy
Treatment
Daily image verification (kV or Cone beam CT)
Stereotactic Technique
Tumours of the liver move over 3 cm and can change in size or shape during the respiratory cycle. They are usually not visible on non-contrast CT (including cone-beam CT). This makes identification of the tumour location difficult. Two methods to improve targeting include:
- Using surrogate landmarks near the tumour (eg. diaphragm for superior liver tumours, surgically placed fiducial markers)
- Using breathing control methods (abdominal compression,
4D CT is essential for accurate mapping of tumour position.
Kirsty Brock
Pre-Simulation
Obtain informed consent.
Simulation
Positioning
Patient lies supine on whole body vacuum bag.
Immobilisation
Whole body vacuum bag. Arms raised above head (wingboard).
Important to limit tumour movement to < 5 mm; consider abdominal compression.
Data Acquisition
4D CT mandantory for stereotactic treatment, with contrast.
Planning
Volumes
GTV = Contrast-enhanced tumour (during arterial phase), recorded at several periods of respiration
ITV = Combined volumes of GTV at various phases of respiration
PTV = 0.3 - 0.5 cm expansion
Dose
Varies considerably in the literature. Popular fractionation is 8 Gy x 6 fractions (48 Gy total), which attempts to reduce toxicity compared to more hypofractionated methods (eg. 36 in 3).
Dose is prescribed to the 80% isodose line; accepting much higher dose to the centre of the GTV.
Fractions are delivered at least 48 hours apart.
Normal Dose Constraints
Varies according to the dose/fractionation schedule. For 8-9 Gy in 6 fractions:
- Mean liver GTV dose < 22 Gy
- Stomach < 30 Gy
- Duodenum < 30 Gy
- Bowel < 30 Gy
- Oesophagus < 30 Gy
- Spinal cord < 27 Gy
- Kidney mean < 12 Gy
- Heart volume 1 cm3 < 40 Gy
Normal liver mean dose < 13 Gy with 36 in 3 fractions.
