A phase I study of weekly doxorubicin and oral topotecan for patients with relapsed or refractory small cell lung cancer (SCLC): A Fred and Pamela Buffet Cancer Center Clinical Trials Network study

•Topotecan and doxorubicin provide sequential topoisomerase I and II inhibition.•Hematologic side effects were the most common. There were no therapy-related grade 5 toxicities.•The maximum tolerated dose of oral topotecan was 1.35 mg/m2.•The response rate was 20% (4/20); median PFS and OS were 3.6 months and 6 months, respectively.•The combination of topotecan and doxorubicin is safe and effective in relapsed SCLC. Relapsed/refractory small cell lung cancer (SCLC) has a poor prognosis, with no good options. We evaluated a novel combination of topotecan and doxorubicin, providing sequential topoisomerase I and II inhibition, in this setting. Adult patients (>19 years) with relapsed/refractory SCLC, who had received at least one prior chemotherapy regimen were eligible. Patients received escalating doses of oral topotecan on days 1–5 of each three week cycle (maximum - 5 cycles). The dosing cohorts were: 0.85 mg/m2, 1.05 mg/m2, 1.35 mg/m2, 1.65 mg/m2 and 2.30 mg/m2. All patients received weekly doxorubicin 20 mg/m2 intravenously starting day 6 of the first cycle and continued weekly for a maximum of 15 weeks. In the absence of pre-specified dose limiting toxicities (DLT), patients were enrolled serially to escalated dose level cohorts. Twenty-two patients were enrolled, of which 20 were evaluable. Median age was 61 years; 74% were male and 95% were Caucasian. Hematologic side effects were the most common adverse events. There were no therapy-related Grade 5 toxicities. Incidence of DLT based on cohorts were: DL2: 1/6 (Grade 4 thrombocytopenia), DL3: 1/6 (AST elevation) and DL4: 2/4 (Grade 4 thrombocytopenia). Response rate was 20% (4/20) and disease control rate (SD + PR) was 36%. The median progression free and overall survival were 3.6 months and 6 months, respectively. The combination of topotecan and doxorubicin was safe and effective in relapsed/refractory SCLC. The maximum tolerated dose of oral topotecan was 1.35 mg/m2 when given concurrently with weekly doxorubicin.