A therapeutic composition for treatment of cancer in a mammal is disclosed. The composition comprises an effective amount of a yeast beta-glucan composition which is suitable for oral administration and for absorption through the gastrointestinal tract of the mammal. The above therapeutic composition may further comprise antitumor antibodies or cancer vaccine composition, wherein the antitumor activities of the antitumor antibodies or the cancer vaccine composition are enhanced by the yeast glucan.
