 Gastrointestinal stromal tumors (GIST) are known to withstand cancer chemotherapy treatment and do not respond to any kind of therapy (in 2001) in advanced cases.However, tyrosine kinase inhibitor STI571 (imatinib) is effective in the treatment of patients with metastatic gastrointestinal stromal tumors.Gastrointestinal stromal tumors consist of a cluster of mesenchymal neoplasms that are formed from precursors to cells that make up the connective-tissue in the gastrointestinal tract.