title: Imatinib plasma levels during successful long-term treatment of metastatic-gastrointestinal stromal tumors.
abstract: OBJECTIVE
  To investigate whether imatinib dosage correlated with effective plasma levels and clinical characteristics for Japanese patients undergoing long-term (≥2 years) imatinib therapy for GISTs.
  
  
  METHODS
  Twenty-five patients who received imatinib for a metastatic pathologically diagnosed GISTs at our hospital were enrolled. Imatinib response was assessed according to Choi’s criteria. Blood samples were collected 22–26 h after the previous imatinib dose before the next scheduled dose. Results: Fourteen patients were male and the median age was 65 years. The median duration of imatinib therapy was 3.8 years (range, 2.0–11.5 years). The median plasma level of imatinib was 1098 ng/ml and the minimal plasma level after ≥5 years of therapy was 789 ng/ml. Imatinib dosage was significantly correlated with history of gastrectomy. The minimum body surface area of patients who received 400-mg/day imatinib dosage was 1.560 m2.
  
  
  CONCLUSIONS
  The minimum level in all patients showing response for ≥5 years of treatment was 789 ng/ml, suggesting an effective plasma imatinib level of ≥800 ng/ml. Our results suggest that imatinib dosage of 400 mg/day is recommended for a patient with a large BSA (≥1.56 m2) and that of 300 mg/day might be sufficient for patients who have undergone a gastrectomy.
authors.forename: Akira
authors.initials: A
authors.lastname: Sawaki
authors.forename: Kazuki
authors.initials: K
authors.lastname: Inaba
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nomura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kanie
authors.forename: Tomonori
authors.initials: T
authors.lastname: Yamada
authors.forename: Katsumi
authors.initials: K
authors.lastname: Hayashi
authors.forename: Makoto
authors.initials: M
authors.lastname: Okawaki
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamamura
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Hirai
authors.forename: Etsuro
authors.initials: E
authors.lastname: Orito
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D001549:Benzamides / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D001830:Body Surface Area; D017024:Chemotherapy, Adjuvant; D004334:Drug Administration Schedule; D054796:Drug Dosage Calculations; D016903:Drug Monitoring; D005260:Female; D005743:Gastrectomy; D046152:Gastrointestinal Stromal Tumors / Q000097:blood / Q000188:drug therapy* / Q000556:secondary*; D006801:Humans; D000068877:Imatinib Mesylate; D007564:Japan; D008297:Male; D008875:Middle Aged; D010879:Piperazines / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D011743:Pyrimidines / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D013274:Stomach Neoplasms / Q000097:blood / Q000188:drug therapy* / Q000473:pathology*; D016896:Treatment Outcome
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D000068877:Imatinib Mesylate