Radiotherapy

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.


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