International audience; BACKGROUND: All randomised phase 3 studies of selective internal radiation therapy for advanced hepatocellular carcinoma published to date have reported negative results. However, these studies did not use personalised dosimetry. We aimed to compare the efficacy of a personalised versus standard dosimetry approach of selective internal radiation therapy with yttrium-90-loaded glass microspheres in patients with hepatocellular carcinoma.METHODS: DOSISPHERE-01 was a randomised, multicentre, open-label phase 2 trial done at four health-care centres in France. Patients were eligible if they were aged 18 years or older and had unresectable locally advanced hepatocellular carcinoma, at least one measurable lesion 7 cm or more in size, a hepatic reserve of at least 30% after selective internal radiation therapy, no extrahepatic spread (other than to the lymph nodes of the hilum, with a lesion 5% of patients) grade 3 or higher adverse events were ascites (one [3%] patient who received personalised dosimetry vs two [10%] patients who received standard dosimetry), hepatic failure (two [6%] vs none), lymphopenia (12 [34%] vs nine [43%]), increased aspartate aminotransferase concentrations (three [9%] vs two [10%]), increased alanine aminotransferase concentrations (three [9%] vs none), anaemia (two [6%] vs one [5%]), gastrointestinal haemorrhage (none vs two [10%]), and icterus (none vs two [10%]). One treatment-related death occurred in each group.INTERPRETATION: Compared with standard dosimetry, personalised dosimetry significantly improved the objective response rate in patients with locally advanced hepatocellular carcinoma. The results of this study suggest that personalised dosimetry is likely to improve outcomes in clinical practice and should be used in future trials of selective internal radiation therapy. FUNDING: Biocompatibles UK, a Boston Scientific Group company.