Primary Liver Cancer: Radiation Therapy Planning
The development of modern radiotherapy planning and delivery techniques has enabled safe and effective delivery of tumoricidal doses of liver-directed radiotherapy. With more refined assessments of hepatotoxicity risk, an increasing number of patients wit
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Florence K. Keane and Theodore Hong
10.1 R adiation Treatment for HCC and ICC • Advances in radiotherapy treatment planning and delivery allow the safe delivery of tumoricidal doses of radiotherapy with minimal associated toxicity. • We recommend liver-directed RT in patients who are not candidates for orthotopic liver transplantation, surgical resection, or radiofrequency ablation, including patients with one or multiple lesions measuring 3–6 cm or patients with larger tumors (6–10 cm) with a sufficient volume of normal hepatic parenchyma. –– Select patients with tumor vein thrombosis with adequate hepatic function can be safely treated with liver-directed RT. –– Patients with Child-Pugh Class C cirrhosis should not be treated off-protocol.
10.2 Treatment Planning 10.2.1 Simulation • Computed tomography (CT) or magnetic resonance (MR)-based simulation. F.K. Keane, MD • T. Hong, MD (*) Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA e-mail: [email protected]
–– Four-dimensional CT (4D-CT) is needed to assess motion. • Patients are simulated supine with arms up. • Immobilization devices are used and may include thermoplastic devices or vacuum bags, with or without a body frame [1]. • Patients receive both oral and multiphasic intravenous (IV) contrast at the time of simulation.
10.3 Target Identification • Both HCC and ICC have variable enhancement patterns on CT and MRI. Multiphasic intravenous (IV) contrast with arterial, portal venous, and delayed phase is needed for accurate tumor identification, as use of only one phase of contrast for target identification increases the risk of undercontouring of the target or inclusion of normal hepatic parenchyma or vasculature in the target volume. Tumor vascular invasion further complicates target identification [2]. –– HCC classically exhibits rapid arterial enhancement with washout on delayed phases [3, 4], but enhancement varies based on tumor size and perfusion [4–7]. Fig. 10.1 and Fig. 10.2 • Larger nodules may have a fibrous capsule which results in delayed enhancement and washout of contrast [4], while
© Springer International Publishing AG 2017 T. Hong, P. Das (eds.), Radiation Therapy for Gastrointestinal Cancers, DOI 10.1007/978-3-319-43115-4_10
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Fig. 10.1 Hepatocellular carcinoma with best visualization in the arterial phase. Lesion one shows arterial enhancement (a) and venous washout (b). Lesion two also shows arterial enhancement (c) and venous washout (d)
diffuse-type HCC often has minimal arterial enhancement [5]. Tumor venous thrombosis and vascular involvement may further alter enhancement patterns. • On MRI, larger HCC nodules may be hyperintense on T2 series and hypointense on T1 series, while smaller nodules may be T1 isointense before rapid but transient contrast enhancement [8, 9]. • RTOG consensus guidelines recommend contouring the gross tumor volume (GTV) as the union of GTVs across all phases of imaging [2]. This ensures accurate ide
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