Abstract
BackgroundSeveral radiotherapeutic approaches for patients with oligotopic malignant liver lesions unfit for surgical resection exist. The most advanced competitive techniques are high-dose-rate (HDR) brachytherapy, Cyberknife, volume-modulated-arc therapy (VMAT) and Tomotherapy. We evaluated the optimal technique by a planning study for a single ablative dose with different lesion sizes.MethodsWe compared dose distributions of HDR-brachytherapy with stereotactic ablative radiotherapy using the Cyberknife, VMAT or Tomotherapy. Tumor-control-probabilities (TCP), normal-tissue-complication-probabilities (NTCP) were determined in a theoretical framework applying a single dose of 20 Gy (demanding 95% coverage) for intrahepatic lesions of 1–5 cm in size. We evaluated therapeutic ratios by TCP (mean dose in the lesion) relative to high-dose (conformality) or low-dose liver exposition in dependency on the lesion size for each technique. In addition, we considered treatment times and accuracy (clinical target volume vs planning target volume).ResultsHDR-brachtherapy has the highest therapeutic ratios with respect to high-dose as well as low-dose liver exposition even for extended lesions, and the Cyberknife being suited second best. However, for lesions ≥ 3 cm diameter the therapeutic ratios of all ablative techniques are increasingly converging, and better tolerance and shorter treatment times of noninvasive external techniques become more important. On the other hand, mean tumor doses of HDR-brachytherapy of near 60 Gy are unattainable by the other techniques gaining only 22–34 Gy, and the conformality of HDR-brachytherapy is still rather good for lesions ≥ 3 cm diameter.ConclusionsHDR-brachytherapy is by far the most effective technique to treat intrahepatic lesions by a single fraction, but sparing of the surroundings declines with increasing lesion size and approaches the benchmarks of external beam radiosurgery techniques. External beam radiotherapy has the advantage to use suitable fractionation schedules.
Highlights
Several radiotherapeutic approaches for patients with oligotopic malignant liver lesions unfit for surgical resection exist
A variety of modern external beam radiation techniques are available using dedicated linear accelerators, competing with the interstitial rather accurate but invasive method. This includes intensity modulation radiotherapy (IMRT), rotational techniques such as volume modulated arc therapy (VMAT) or Tomotherapy and the Cyberknife, which are suitable for radiosurgery in a single fraction [3, 11]
We focus on oligotopic malignant liver lesions that are treated in a single fraction as this is a logistical and practical advantage for the patient, without evidence of improved oncological outcome compared to fractionated schedules
Summary
Several radiotherapeutic approaches for patients with oligotopic malignant liver lesions unfit for surgical resection exist. Wust et al Radiat Oncol (2021) 16:51 treatment strategies for patients with oligotopic malignant liver lesions are warranted to complement systemic therapies in cases not qualifying for surgical resection [3, 5]. Image-guided high-dose-rate interstitial (HDR-) brachytherapy uses an iridium-192 source of < 1 mm diameter, which is moved in an implanted catheter array according to a treatment plan in order to generate an optimal dose distribution for a specified target volume and adjacent organs of risk. A variety of modern external beam radiation techniques are available using dedicated linear accelerators, competing with the interstitial rather accurate but invasive method This includes intensity modulation radiotherapy (IMRT), rotational techniques such as volume modulated arc therapy (VMAT) or Tomotherapy and the Cyberknife, which are suitable for radiosurgery in a single fraction [3, 11]
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