title: Pharmacogenetic study in rectal cancer patients treated with preoperative chemoradiotherapy: polymorphisms in thymidylate synthase, epidermal growth factor receptor, GSTP1, and DNA repair genes.
abstract: OBJECTIVE
  Several studies have been performed to evaluate the usefulness of neoadjuvant treatment using oxaliplatin and fluoropyrimidines for locally advanced rectal cancer. However, preoperative biomarkers of outcome are lacking. We studied the polymorphisms in thymidylate synthase, epidermal growth factor receptor, glutathione S-transferase pi 1 (GSTP1), and several DNA repair genes to evaluate their usefulness as pharmacogenetic markers in a cohort of 128 rectal cancer patients treated with preoperative chemoradiotherapy.
  
  
  METHODS
  Blood samples were obtained from 128 patients with Stage II-III rectal cancer. DNA was extracted from the peripheral blood nucleated cells, and the genotypes were analyzed by polymerase chain reaction amplification and automated sequencing techniques or using a 48.48 dynamic array on the BioMark system. The germline polymorphisms studied were thymidylate synthase, (VNTR/5'UTR, 2R G>C single nucleotide polymorphism [SNP], 3R G>C SNP), epidermal growth factor receptor (Arg497Lys), GSTP1 (Ile105val), excision repair cross-complementing 1 (Asn118Asn, 8092C>A, 19716G>C), X-ray repair cross-complementing group 1 (XRCC1) (Arg194Trp, Arg280His, Arg399Gln), and xeroderma pigmentosum group D (Lys751Gln). The pathologic response, pathologic regression, progression-free survival, and overall survival were evaluated according to each genotype.
  
  
  RESULTS
  The ∗3/∗3 thymidylate synthase genotype was associated with a greater response rate (pathologic complete remission and microfoci residual tumor, 59% in ∗3/∗3 vs. 35% in ∗2/∗2 and ∗2/∗3; p=.013). For the thymidylate synthase genotype, the median progression-free survival was 103 months for the ∗3/∗3 patients and 84 months for the ∗2/∗2 and ∗2/∗3 patients (p=.039). For XRCC1 Arg399Gln SNP, the median progression-free survival was 101 months for the G/G, 78 months for the G/A, and 31 months for the A/A patients (p=.048).
  
  
  CONCLUSIONS
  The thymidylate synthase genotype and XRCC1 Arg399Gln polymorphism might help to identify Stage II-III rectal cancer patients with a better outcome after preoperative concomitant chemoradiotherapy.
authors.affiliation: Department of Medical Oncology, Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona, Barcelona, Spain. dpaez@santpau.cat
authors.forename: David
authors.initials: D
authors.lastname: Páez
authors.forename: Juliana
authors.initials: J
authors.lastname: Salazar
authors.forename: Laia
authors.initials: L
authors.lastname: Paré
authors.forename: Lourdes
authors.initials: L
authors.lastname: Pertriz
authors.forename: Eduardo
authors.initials: E
authors.lastname: Targarona
authors.forename: Elisabeth
authors.initials: E
authors.lastname: del Rio
authors.forename: Agusti
authors.initials: A
authors.lastname: Barnadas
authors.forename: Eugenio
authors.initials: E
authors.lastname: Marcuello
authors.forename: Montserrat
authors.initials: M
authors.lastname: Baiget
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D059248:Chemoradiotherapy; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D018572:Disease-Free Survival; D066246:ErbB Receptors / Q000235:genetics*; D005260:Female; D005819:Genetic Markers / Q000235:genetics; D005838:Genotype; D051549:Glutathione S-Transferase pi / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D018365:Neoplasm, Residual; D019990:Perioperative Care; D011110:Polymorphism, Genetic; D012004:Rectal Neoplasms / Q000235:genetics* / Q000401:mortality / Q000473:pathology / Q000628:therapy; D012074:Remission Induction; D013940:Thymidylate Synthase / Q000235:genetics*; D000076105:X-ray Repair Cross Complementing Protein 1; D051759:Xeroderma Pigmentosum Group D Protein / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; D005819:Genetic Markers; D000076105:X-ray Repair Cross Complementing Protein 1; C000619371:XRCC1 protein, human; D013940:Thymidylate Synthase; D051549:Glutathione S-Transferase pi; D066246:ErbB Receptors; D051759:Xeroderma Pigmentosum Group D Protein