Viability of cancer cells (e.g., hepatocellular carcinoma cells) can be reduced by administering sorafenib to the cancer cells and applying an alternating electric field with a frequency between 100 and 400 kHz to the cancer cells. Viability of cancer cells (e.g., hepatocellular carcinoma cells) disposed in a body of a living subject can be reduced by administering sorafenib to the subject and applying an alternating electric field with a frequency between 100 and 400 kHz to the cancer cells. Notably, experiments show that the combination of sorafenib and the alternating electric field produces synergistic results both in vitro and in vivo.