title: Allelic imbalance at p53 and microsatellite instability are predictive markers for resistance to chemotherapy in gastric carcinoma.
abstract: BACKGROUND
  Combined treatment with 5-fluorouracil and cisplatin (FP chemotherapy) is an effective neoadjuvant regimen for gastric carcinoma. However, it is ineffective in half of all patients. This study tests the hypothesis that genetic markers might identify those patients with gastric cancer who would respond to neoadjuvant FP chemotherapy.
  
  
  METHODS
  A total of 23 patients with gastric carcinoma were treated with neoadjuvant chemotherapy. Pretreatment biopsy specimens before neoadjuvant chemotherapy were obtained from 15 of 23 patients, and resected tumors were obtained from all 23. Genetic studies were performed to detect allelic imbalance (AI), microsatellite instability (MSI), and K-ras mutation.
  
  
  RESULTS
  A clinical response was observed in 13 of 23 patients. Kaplan-Meier survival curve showed that clinical responder group had a significantly higher likelihood of overall survival (P = 0.0165), compared with nonresponder group. In 23 resection specimens, 10 of 23 tumors presented AI at the p53 locus and/or MSI; 8 of the 10 tumors were nonresponders, while 12 of 13 tumors without p53 AI or MSI were responders (P = 0.0007). In 15 pretreatment biopsy specimens, 8 tumors had p53 AI and/or MSI; 7 of the 8 tumors were nonresponders, while 6 of 7 tumors without p53 AI or MSI were responders to preoperative chemotherapy (P = 0.008). Tumors with AI at the p53 locus and/or MSI were significantly more resistant to neoadjuvant chemotherapy. No relationship was found between K-ras mutations and responses.
  
  
  CONCLUSIONS
  Analysis for p53 AI and MSI might represent a clinically useful approach to predicting the response to neoadjuvant FP chemotherapy in gastric carcinoma.
authors: Department of Surgical Oncology, Osaka City University Graduate School of Medicine, Osaka, Japan. m9312510@med.osaka-cu.ac.jp
authors: Masakazu
authors: M
authors: Yashiro
authors: Toru
authors: T
authors: Inoue
authors: Nobuaki
authors: N
authors: Nishioka
authors: Tasuku
authors: T
authors: Matsuoka
authors: C Richard
authors: CR
authors: Boland
authors: Kosei
authors: K
authors: Hirakawa
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D022981:Allelic Imbalance / Q000235:genetics*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000235:genetics; D002945:Cisplatin / Q000008:administration & dosage; D019008:Drug Resistance, Neoplasm; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage; D011905:Genes, ras; D006801:Humans; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D020360:Neoadjuvant Therapy; D009367:Neoplasm Staging; D016133:Polymerase Chain Reaction; D011379:Prognosis; D013274:Stomach Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D015996:Survival Rate; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
chemical_list: D014408:Biomarkers, Tumor; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D002945:Cisplatin; D005472:Fluorouracil