The invention relates to treating colorectal polyps and precancercerous colorectal changes by topical administration of immunomodulating drugs of the imidazoquinoline family, such as imiquimod (1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4-amine), resiquimod (4-amino-α,α-dimethyl-2-ethoxymethyl-1H-imidazo[4,5-c]quinoline-1-ethanol), sotirimod (2-methyl-1-(2-methylpropyl)-1H-imidazo[4,5-c][1,5]naphthyridin-4-amine).