title: Radiotherapy for hepatocellular carcinoma: systematic review of radiobiology and modeling projections indicate reconsideration of its use.
abstract: OBJECTIVE
  External beam radiotherapy currently has a limited role in the treatment of hepatocellular carcinoma (HCC). The purpose of this article was to review available radiobiological data on HCC and normal liver and incorporate these data into radiobiological models that may be used to explain and improve treatment.
  
  
  METHODS
  Volume doubling times of HCC were described and used to demonstrate growth of HCC with time, assuming both exponential and logistic growth. Radiosensitivity of HCC was described and used to demonstrate the probability of uncomplicated tumor control as tumor size increases. The relationship between tolerance of liver to irradiation and volume irradiated was examined.
  
  
  RESULTS
  The median volume doubling time for untreated HCC was 130 days. HCC have a long period of subclinical growth. Radiosensitivity of HCC lies within the range of other tumors commonly treated with radiotherapy. When treating small volumes of normal liver, relatively high doses may be used with low risk of late radiation damage. There is a high probability of sterilizing subclinical disease and small HCC with tolerable radiation doses.
  
  
  CONCLUSIONS
  New radiobiological data, modeling, emerging clinical data and the advantages offered by standard external beam radiotherapy techniques suggest the need for reconsidering the use of radiotherapy and for new trials.
authors.affiliation: Hepatology and Liver Transplant Medicine Unit, Flinders Medical Centre, Adelaide, South Australia, Australia. alan.wigg@health.sa.gov.au
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Wigg
authors.forename: Kevin
authors.initials: K
authors.lastname: Palumbo
authors.forename: David R
authors.initials: DR
authors.lastname: Wigg
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000473:pathology / Q000532:radiotherapy*; D049109:Cell Proliferation / Q000528:radiation effects*; D019317:Evidence-Based Medicine; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D008954:Models, Biological; D011836:Radiation Tolerance; D011878:Radiotherapy / Q000009:adverse effects; D013997:Time Factors; D016896:Treatment Outcome; D047368:Tumor Burden