Fig. 28.

Expected treatment response after stereotactic body radiotherapy (SBRT) and transarterial radioembolization (TARE). Axial contrast-enhanced CT of the liver obtained in late arterial phase are illustrated: a Pretreatment: typically used for bridging, debulking, or palliative treatment in patients with intermediate- to advanced-stage hepatocellular carcinoma. May be used alone or in combination with other treatments. SBRT may be used as an alternative to RFA for early-stage HCC. With SBRT, lesions should be located away from critical organs. Before TARE, ^99mTc-MAA scan is performed to determine radiation dose to be delivered to tumor/non-tumor areas and identify shunting. b 1–3 months posttreatment: intralesional nodular arterial phase hyperenhancement and washout may persist but should gradually fade as radiation necrosis progresses. Geographic enhancing region surrounding the treated zone may represent inflammatory hyperemia, venous congestion, and radiation fibrosis and could be misinterpreted as infiltrative disease. With SBRT, tumor size and enhancement may transiently increase during the first weeks posttreatment, a phenomenon called pseudoprogression. c ≥ 6 months posttreatment: treated zone shrinks as fibrosis progresses and is associated with capsular retraction. Intralesional enhancement and washout appearance may persist but usually resolves after 6 months. Late venous enhancement in the irradiated non-tumorous parenchyma may still be observed. Washout may help differentiate radiation-induced changes from tumor progression. An increase in enhancement or in washout appearance after an initial favorable response suggests recurrence