title: Evaluation of intravenous 6-thioguanine as first-line chemotherapy in women with metastatic breast cancer.
abstract: 6-Thioguanine (6-TG) is a purine analog that has marked variability in plasma concentration after oral administration. Following the development of a multiple-day i.v. regimen, we performed a phase II trial of this agent as first-line chemotherapy in women with metastatic breast cancer. Forty-one patients with measurable (31 patients) or evaluable (10 patients) disease were entered into this trial. 6-TG was administered i.v. over a 10 min period daily for 5 consecutive days, with a planned cycle length of 35 days. The daily dosage level was 55 mg/m2 in the first 15 patients, but this was increased to 65 mg/m2 in the remaining patients due to inadequate myelosuppression at the lower dose. Six patients, all with measurable disease, achieved a complete response (CR) (two patients) or a partial response (PR) (four patients). Three responses occurred at the 55 mg/m2 level and three at the 65 mg/m2 level. The 95% confidence interval (CI) for the true response rate among patients with measurable disease was 6-39%. The median time to progression was 140 days and median survival time was 460 days. The regimen was well tolerated. We conclude that 6-TG, as given in this study, has limited activity as first-line chemotherapy for women with metastatic breast cancer.
authors.affiliation: Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.
authors.forename: J N
authors.initials: JN
authors.lastname: Ingle
authors.forename: D I
authors.initials: DI
authors.lastname: Twito
authors.forename: V J
authors.initials: VJ
authors.lastname: Suman
authors.forename: J E
authors.initials: JE
authors.lastname: Krook
authors.forename: J A
authors.initials: JA
authors.lastname: Maillard
authors.forename: H E
authors.initials: HE
authors.lastname: Windschitl
authors.forename: R F
authors.initials: RF
authors.lastname: Marschke
mesh_terms: D000328:Adult; D000368:Aged; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D008875:Middle Aged; D009362:Neoplasm Metastasis; D012074:Remission Induction; D016019:Survival Analysis; D013866:Thioguanine / Q000008:administration & dosage / Q000627:therapeutic use*
chemical_list: D000964:Antimetabolites, Antineoplastic; D013866:Thioguanine