 Imatinib IM has dramatically improved survival of gastrointestinal stromal tumors GIST. However, most patients become resistant to IM in less than two years. This clinical trial combines targeted therapy IM with immunotherapy peginterferon α-2b. Hypothesis: Apoptosisnecrosis of imatinib-sensitive GIST releases GIST-specific antigens in vivo while Peginterferon α-2b fulfills the role of cytokine signal danger signal, this combination can induce effective innate and adaptive anti-GIST immunity, which can eradicate imatinib-resistant clones and GIST stem cells via recognition of common antigens shared with imatinib-sensitive GIST, leading to improved response rate and remission duration. 