Takahashi H, et al. - In view of the possibility that transarterial chemoembolization (TACE) could be used for selected hepatocellular carcinoma (HCC) patients who have previously undergone proton beam therapy (PBT), researchers investigated the angiographic findings from HCC patients previously treated using PBT and classified the abnormal PBT-related angiographic findings. In addition, they analyzed these factors’ frequency, onset timing, and influence on technical difficulty. Among 31 included patients (28 men and 3 women; mean age: 69 years), they noted four angiographic findings [(1) abnormal staining of the irradiated liver parenchyma, (2) development of tortuous tumor feeder vessels, (3) development of an extrahepatic collateral pathway to the liver, and (4) development of arterioportal (AP) or arteriovenous (AV) shunts] which seemed to be related to the previous PBT. Twenty-two patients displayed abnormal staining of the irradiated liver parenchyma, which obscured the angiographic tumor staining in 4 patients. Thirteen patients developed a tortuous tumor feeder vessel. Seven patients developed an extrahepatic collateral pathway. Four patients developed an arterioportal or arteriovenous shunt. These four findings appeared at different intervals after the PBT. Among patients who underwent a single PBT treatment, abnormal staining of the liver parenchyma (median interval: 477 days) appeared the earliest, AV or AP shunts developed later (median interval: 588 days), tortuous feeder vessels developed even later (median interval: 699 days), and extrahepatic collateral pathways appeared latest (median interval: 917 days). Familiarity with these findings may help in developing appropriate treatment plans for these patients.