A validated proton beam therapy patch-field protocol for effective treatment of large hepatocellular carcinoma

Development of a curative local treatment for large hepatocellular carcinoma (HCC) is an important issue. Here, we investigated the dose homogeneity, safety and antitumor effectiveness of proton beam therapy (PBT) using a patch-field technique for large HCC. Data from nine patients (aged 52–79 years) with large HCC treated with patch-field PBT were investigated. The cranial–caudal diameters of the clinical target volumes (CTVs) were 15.0–18.6 cm (median 15.9). The CTV was divided cranially and caudally while both isocenters were aligned along the cranial–caudal axis and overlap of the cranial and caudal irradiation fields was set at 0–0.5 mm. Multileaf collimators were used to eliminate hot or cold spots. Total irradiation doses were 60–76.4 Gy equivalents. Irradiation doses as a percentage of the prescription dose (from the treatment planning system) around the junction were a minimum of 93–105%, a mean of 99–112%, and a maximum of 105–120%. Quality assurance (QA) was assessed in the cranial and caudal irradiation fields using imaging plates. Acute adverse effects of Grade 3 were observed in one patient (hypoalbuminemia), and a late adverse effect of Grade 3 was observed in one patient (liver abscess). Child–Pugh class elevations were observed in four patients (A to B: 3; B to C: 1). Overall survival rates at 1 and 2 years were 55 and 14%, respectively, with a median overall survival of 13.6 months. No patients showed local recurrence. Patch-field PBT supported by substantial QA therefore is one of the treatment options for large HCC.