[en] The aim of this study was to investigate the feasibility of administering increasing activities of ¹⁸⁸Re-4-hexadecyl-1-2,9,9-tetramethyl-4,7-diaza-1,10-decanethiol/lipiodol (¹⁸⁸Re-HDD/lipiodol) for the treatment of hepatocellular carcinoma (HCC) in patients with well-compensated cirrhosis. The activity levels were increased by 1.1 GBq/step after a 6-week interval without unacceptable adverse events in at least five consecutive patients. Absorbed doses to the various organs were calculated according to the MIRD formalism, based on three gamma-scintigraphic studies. Response was assessed by means of MRI and alpha-fetoprotein (AFP) monitoring. Thirty-five treatments were carried out in 28 patients. Activities from 4.8 to 7.0 GBq ¹⁸⁸Re-HDD/lipiodol were administered via a transfemoral catheter. The mean absorbed dose to the liver (including tumour) was 7.6±2.2, 9.8±4.9 and 15.2±4.9 Gy for the 4.8-, 5.9- and 7.0-GBq groups, respectively. Treatment was well tolerated at all activity levels. Further escalation of the administered activity was not feasible owing to limitations related to the radiolabelling procedure. Response assessment on MRI showed partial response, stable disease and disease progression in 1, 28 and 2 assessable treatments, respectively. In 8 of 17 treatment sessions with an initially elevated AFP, a reduction ranging from 19% to 97% was observed 6 weeks later. (orig.)