title: Clinical impact of microsatellite instability in colon cancer following adjuvant FOLFOX therapy.
abstract: OBJECTIVE
  Colon cancer with DNA mismatch repair (MMR) defects reveals indistinguishable clinical and pathologic aspects, including better prognosis and reduced response to 5-fluorouracil (5-FU)-based chemotherapy. There has been no consensus for p53 as a prognostic marker in colorectal cancer. This study investigated the clinical implication of MSI-H/MMR-D and p53 expression in R0-resected colon cancer patients who received adjuvant oxaliplatin/5-FU/leucovorin (FOLFOX) therapy.
  
  
  METHODS
  We analyzed 135 patients, who had been treated by adjuvant chemotherapy containing 5-FU and oxaliplatin (FOLFOX) after curative resection (R0) for colon adenocarcinoma between May 2004 and November 2007. Tumor expression of the MMR proteins, MLH1 and MSH2, was detected by immunohistochemistry (IHC) in surgically resected tumor specimens. MSI was analyzed by polymerase chain reaction (PCR) amplification using fluorescent dye-labeled primers specific for microsatellite loci. Tumors with MMR defects were defined as those demonstrating loss of MMR protein expression (MMR-D) and/or microsatellite instability high (MSI-H) genotype. Expression patterns of p53 were determined in a semiquantitative manner by light microscopy.
  
  
  RESULTS
  There were 13 (9.6%) patients with stage II, 108 (80%) with stage III, and 14 (10.4%) with stage IV. Fourteen patients with stage IV (10.3%) had metastases to liver only, all of whom underwent complete metastasectomy for liver metastases. In total, 134 tumor specimens were genotyped, 115 specimens were tested by IHC and 113 cases had both genotyping and IHC results available for analysis. Genotyping results demonstrated that 12 (9.0%) cases were MSI-H and 122 (91.0%) were MSI-L/S. By IHC, 11 (9.6%) patients were MMR-D and 104 (90.4%) were MMR-I. The methods were in agreement in 108 patients (94.7%). We assessed 114 patients for p53 expression by immunostaining. MMR status was not significantly associated with DFS (P = 0.56) or OS (P = 0.61) in patients with colon cancer (n = 135) receiving adjuvant FOLFOX. According to p53 status, there was also no significant difference for DFS (P = 0.11) and OS (P = 0.94). For patients with genotyping/IHC agreement (n = 108), there was no difference in DFS (P = 0.57) and OS (P = 0.98) between patients with MSI-H/MMR-D and MSI-L/S/MMR-I tumors.
  
  
  CONCLUSIONS
  The MMR status or p53 positivity was not significantly associated with outcomes to FOLFOX as adjuvant chemotherapy in colon cancer patients with R0 resection. Adding oxaliplatin in adjuvant chemotherapy may overcome negative impact of 5-FU on colon cancers with MSI-H/MMR-D.
authors.affiliation: Divisions of Hematology-Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul, South Korea.
authors.forename: Seung Tae
authors.initials: ST
authors.lastname: Kim
authors.forename: Jeeyun
authors.initials: J
authors.lastname: Lee
authors.forename: Se Hoon
authors.initials: SH
authors.lastname: Park
authors.forename: Joon Oh
authors.initials: JO
authors.lastname: Park
authors.forename: Ho Yeong
authors.initials: HY
authors.lastname: Lim
authors.forename: Won Ki
authors.initials: WK
authors.lastname: Kang
authors.forename: Jin Yong
authors.initials: JY
authors.lastname: Kim
authors.forename: Young Ho
authors.initials: YH
authors.lastname: Kim
authors.forename: Dong Kyung
authors.initials: DK
authors.lastname: Chang
authors.forename: Poong-Lyul
authors.initials: PL
authors.lastname: Rhee
authors.forename: Dae Shick
authors.initials: DS
authors.lastname: Kim
authors.forename: Haeran
authors.initials: H
authors.lastname: Yun
authors.forename: Yong Beom
authors.initials: YB
authors.lastname: Cho
authors.forename: Hee Cheol
authors.initials: HC
authors.lastname: Kim
authors.forename: Seong Hyeon
authors.initials: SH
authors.lastname: Yun
authors.forename: Woo Yong
authors.initials: WY
authors.lastname: Lee
authors.forename: Ho-Kyung
authors.initials: HK
authors.lastname: Chun
authors.forename: Young Suk
authors.initials: YS
authors.lastname: Park
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy* / Q000235:genetics* / Q000601:surgery; D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017024:Chemotherapy, Adjuvant; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000601:surgery; D003131:Combined Modality Therapy; D053843:DNA Mismatch Repair; D005260:Female; D005472:Fluorouracil / Q000627:therapeutic use; D005819:Genetic Markers; D005838:Genotype; D006801:Humans; D007150:Immunohistochemistry; D002955:Leucovorin / Q000627:therapeutic use; D008297:Male; D053842:Microsatellite Instability / Q000187:drug effects*; D008875:Middle Aged; D009944:Organoplatinum Compounds / Q000627:therapeutic use; D011379:Prognosis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016019:Survival Analysis; D016159:Tumor Suppressor Protein p53 / Q000235:genetics
chemical_list: D005819:Genetic Markers; D009944:Organoplatinum Compounds; D016159:Tumor Suppressor Protein p53; D002955:Leucovorin; D005472:Fluorouracil