Evaluation of intravenous 6-thioguanine as first-line chemotherapy in women with metastatic breast cancer

• Published in: American journal of clinical oncology Vol. 20; no. 1; p. 69
• Main Authors: Ingle, J N, Twito, D I, Suman, V J, Krook, J E, Maillard, J A, Windschitl, H E, Marschke, Jr, R F
• Format: Journal Article
• Language: English
• Published: United States 01.02.1997
• Subjects: Adult; Aged; Antimetabolites, Antineoplastic - administration & dosage; Antimetabolites, Antineoplastic - therapeutic use; Breast Neoplasms - drug therapy; Breast Neoplasms - pathology; Drug Administration Schedule; Female; Humans; Middle Aged; Neoplasm Metastasis; Remission Induction; Survival Analysis; Thioguanine - administration & dosage; Thioguanine - therapeutic use
• ISSN: 0277-3732
• DOI: 10.1097/00000421-199702000-00015

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.