Abstract: ObjectiveTo define the maximum-tolerated dose(MTD) and observe the toxicity and clinical practicality of escalation of topotecan combined whole brain radiotherapy for brain metastasis of lung cancer. MethodsEighteen Chinese patients suffering from brain metastasis of lung cancer received conventional fractionation radiotherapy，with 5 daily fractions of 2 Gy per week，the total radiation dose 40 Gy and the larger add to 50～60 Gy. The starting dose of topotecan was 1.0 mg/m²，Escalation dose was 0.25 mg/m²，Every cohort contained at least 3 patients.If no dose-limiting toxicity(DLT) was observed，the next dose level was opened for entry.These courses were repeated until DLT appeared.MTD was declared as one dose level below which DLT appeared. ResultsDLT was defined as grade 3 matologic toxicity at the level of topotecan 2.0 mg/m²，The major side effects were matologic toxicity ，nausea and vomiting. ConclutionCombined whole brain radiotherapy and topotecan for brain metastasis from lung cancer is well tolerted. The maximun tolerated dose of topotecan was 1.75 mg/m².