[Antitumor activity by long-term administration of low-dose etoposide]

Antitumor activity by long term administration of low dose etoposide (ETP) was investigated in mice. In a spontaneous metastasis system, intraperitoneal consecutive administration of ETP at 2 mg/kg/day inhibited the number of metastatic nodules of Lewis lung carcinoma in the lung and showed a greater activity than 5-fluorouracil (5-FU) at the dose of 5 mg/kg/day. Alternative administration of ETP and 5-FU also exhibited the anti-metastatic activity, but mean survival time of mice was similar in all of these groups. Mean survival time of ETP-treated mice was prolonged when administration interval was shortened. Also in an artificial metastasis system, ETP inhibited metastasis of Lewis lung carcinoma in the lung. ETP showed antitumor activity against Colon adenocarcinoma 38 as 5-FU, when drugs were administered orally for long term, and the activity did not declined during the experimental period. These results suggest that long term administration of low dose ETP is clinically useful for post-operative and maintenance chemotherapy.