title: Clinical significance of pathological complete response in patients with metastatic gastrointestinal stromal tumors after imatinib mesylate treatment--lessons learned.
abstract: OBJECTIVE
  Imatinib mesylate (IM) has substantial efficacy in patients with metastatic gastrointestinal stromal tumors (GISTs), and pathological complete response (pCR) following IM treatment has been sporadically reported; however, its clinical significance for GIST needs to be clarified.
  
  
  METHODS
  From 2001 to 2010, 26 out of 171 patients with metastatic GIST who received IM with response or stable disease underwent operation. Among them, 12 operations with pCR were compared to 14 operations without pCR regarding clinicopathological features, mutation status, progression-free survival (PFS), and overall survival (OS). Following the operation, each tumor was assessed immunohistologically, and genetic analysis was performed on the tumor tissue.
  
  
  RESULTS
  Twelve out of 26 (46.2%) patients with metastatic GIST who received IM with response or stable disease had pCR. After a median follow-up of 40.8 months, patients with pCR had significantly better PFS and OS than those without pCR [2-year PFS and OS: 82.5% and 100% versus 35.6% and 49.4%, (p=0.014 and p=0.004) respectively]. Predictive factors for pCR were: origin of GIST, response after IM therapy, and duration of IM use before operation. Patients without pCR had a significantly higher frequency of secondary mutation when compared to those with pCR (47.4% versus 0%; p=0.004).
  
  
  CONCLUSIONS
  Patients with colorectal GIST receiving IM who responded more quickly to IM treatment prior to surgery had a higher chance of pCR. pCR results in significantly favorable PFS and OS, however, IM cannot be withdrawn. Patients without pCR had a significantly higher frequency of secondary mutation when compared to those with pCR.
authors.affiliation: GIST Team, Department of Surgery, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan, R.O.C.
authors.forename: Chi-Tung
authors.initials: CT
authors.lastname: Cheng
authors.affiliation: GIST Team, Department of Surgery, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan, R.O.C.
authors.forename: Chun-Yi
authors.initials: CY
authors.lastname: Tsai
authors.affiliation: GIST Team, Department of Surgery, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan, R.O.C. chen.y9964@gmail.com yehchunnan@gmail.com.
authors.forename: Chun-Nan
authors.initials: CN
authors.lastname: Yeh
authors.affiliation: GIST Team, Department of Surgery, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan, R.O.C.
authors.forename: Kun-Chun
authors.initials: KC
authors.lastname: Chiang
authors.affiliation: Division of Hematology and Oncology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan, R.O.C. chen.y9964@gmail.com yehchunnan@gmail.com.
authors.forename: Yen-Yang
authors.initials: YY
authors.lastname: Chen
authors.affiliation: GIST Team, Department of Surgery, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan, R.O.C.
authors.forename: Shang-Yu
authors.initials: SY
authors.lastname: Wang
authors.affiliation: GIST Team, Department of Surgery, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan, R.O.C.
authors.forename: Tsung-Wen
authors.initials: TW
authors.lastname: Chen
authors.affiliation: Department of Radiology, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan, R.O.C.
authors.forename: Jeng-Hwei
authors.initials: JH
authors.lastname: Tseng
authors.affiliation: Department of Pathology, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan, R.O.C.
authors.forename: Shih-Ming
authors.initials: SM
authors.lastname: Jung
authors.affiliation: Department of Pathology, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan, R.O.C.
authors.forename: Tse-Ching
authors.initials: TC
authors.lastname: Chen
authors.affiliation: GIST Team, Department of Surgery, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan, R.O.C.
authors.forename: Ta-Sen
authors.initials: TS
authors.lastname: Yeh
mesh_terms: D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001549:Benzamides / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000378:metabolism; D005260:Female; D005500:Follow-Up Studies; D046152:Gastrointestinal Stromal Tumors / Q000188:drug therapy* / Q000401:mortality / Q000473:pathology*; D006801:Humans; D000068877:Imatinib Mesylate; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009367:Neoplasm Staging; D010879:Piperazines / Q000627:therapeutic use*; D011379:Prognosis; D011446:Prospective Studies; D011743:Pyrimidines / Q000627:therapeutic use*; D012074:Remission Induction; D015996:Survival Rate
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D014408:Biomarkers, Tumor; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate
keywords: Pathological complete response; gastrointestinal stromal tumor; imatinib mesylate