Methods for treating prostate cancer, including advanced prostate cancer, in a subject in need thereof, include administering once-daily to the subject, at least 80 mg of N-(4-(1-(2,6-difluorobenzyl)-5-((dimethylamino)methyl)-3-(6-methoxy-3-pyridazinyl)-2,4-dioxo-1,2,3,4-tetrahydrothieno[2,3-d]pyrimidin-6-yl)phenyl)-N′-methoxyurea, or a corresponding amount of a pharmaceutically acceptable salt thereof. Another method includes: administering once-daily to the subject in need thereof, an oral load dose formulation having from 240 mg to 480 mg of N-(4-(1-(2,6-difluorobenzyl)-5-((dimethylamino)methyl)-3-(6-methoxy-3-pyridazinyl)-2,4-dioxo-1,2,3,4-tetrahydrothieno[2,3-d]pyrimidin-6-yl)phenyl)-N′-methoxyurea, or a corresponding amount of a pharmaceutically acceptable salt thereof; and thereafter administering once-daily to the subject, an oral maintenance dose formulation having 80 mg to 160 mg of N-(4-(1-(2,6-difluorobenzyl)-5-((dimethylamino)methyl)-3-(6-methoxy-3-pyridazinyl)-2,4-dioxo-1,2,3,4-tetrahydrothieno[2,3-d]pyrimidin-6-yl)phenyl)-N′-methoxyurea, or a corresponding amount of a pharmaceutically acceptable salt thereof.