A method for treating a cancer by administering a therapeutically active composition for the treatment in a patient or human thereof, is disclosed. The method according to the present invention, comprises a step of administering to the human a pharmaceutical composition comprising a therapeutic amount of sodium thiosulfate (Na2S2O3) along with at least one of a pharmaceutical carrier and a pharmaceutical excipient. The carriers, or excipients are selected corresponding to the mode of administration to the patient with cancer includes gastric cancer, fibrosarcoma, pancreatic cancer, and head and neck carcinomas. The method further comprises a step of administering the said composition is any one of oral route, intravenous route, inhalation route, intra-vesical route, vaginal route, rectal route, sublingual route, ophthalmic route and topical route.
