title: The role of palliative resection for asymptomatic primary tumor in patients with unresectable stage IV colorectal cancer.
abstract: BACKGROUND
  The prognostic role of surgical resection of primary tumors is not well established in patients with asymptomatic unresectable stage IV colorectal cancer.
  
  
  OBJECTIVE
  The aims of this study were to reveal the prognostic role of surgical resection of primary tumors and to define prognostic factors affecting long-term oncological outcomes in patients with asymptomatic unresectable synchronous metastases.
  
  
  METHODS
  This study was a retrospective analysis of prospectively collected data.
  
  
  METHODS
  Between 2000 and 2008, a total of 416 patients with asymptomatic unresectable stage IV colorectal cancer were analyzed with propensity score matching.
  
  
  METHODS
  Prematching baseline characteristics were compared by bivariate analysis, and 113 pairs were selected after 1:1 matching with propensity scores estimated from logistic regression. The primary end point was overall survival.
  
  
  RESULTS
  Among 416 patients, 218 (52.4%) underwent palliative resection of the primary tumor. Before propensity score matching, palliative resection resulted in a better survival rate than nonresection in univariate analysis (p < 0.001), but not in multivariate analysis (p = 0.08). After matching, the 5-year overall survival rate was significantly lower for patients with peritoneal metastasis and clinical M1b stage tumors in univariate analysis (p = 0.004 and p = 0.02). However, neither peritoneal metastasis nor clinical M1b stage showed any prognostic significance in multivariate analysis. The overall 5-year survival rate of the postmatching group was 4.9% and 3.5% in the palliative resection and nonresection groups. Consequently, palliative resection was not associated with a significant increase in survival compared with nonresection (p = 0.27). A subgroup analysis performed according to the site of metastasis also did not show any significant survival benefit of palliative resection after matching.
  
  
  CONCLUSIONS
  Selection bias and potential confounders were limitations of this study.
  
  
  CONCLUSIONS
  Resection of the primary tumor in patients with asymptomatic unresectable stage IV colorectal cancer was not associated with an improvement in overall survival after propensity score matching.
authors.affiliation: 1Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea 2Department of Surgery, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Jung-A
authors.initials: JA
authors.lastname: Yun
authors.forename: Jung Wook
authors.initials: JW
authors.lastname: Huh
authors.forename: Yoon Ah
authors.initials: YA
authors.lastname: Park
authors.forename: Yong Beom
authors.initials: YB
authors.lastname: Cho
authors.forename: Seong Hyeon
authors.initials: SH
authors.lastname: Yun
authors.forename: Hee Cheol
authors.initials: HC
authors.lastname: Kim
authors.forename: Woo Yong
authors.initials: WY
authors.lastname: Lee
authors.forename: Ho-Kyung
authors.initials: HK
authors.lastname: Chun
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000401:mortality / Q000473:pathology / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D010166:Palliative Care; D010534:Peritoneal Neoplasms / Q000556:secondary; D011183:Postoperative Complications; D011379:Prognosis; D057216:Propensity Score; D012189:Retrospective Studies; D015996:Survival Rate