Efficacy of RAD001/carboplatin in triple-negative metastatic breast cancer: A phase II study.

Abstract

108 Background: Triple-negative breast cancer cells are unable to repair double stranded DNA breaks and have sensitivity to platinum agents. Rapamycin acts synergistically with platinum agents to induce apoptosis and inhibit proliferation in breast cancer cell lines. RAD001 (oral mTOR inhibitor) and Carboplatin combination may have activity in triple-negative breast cancer. Methods: The primary objective is to estimate clinical benefit (complete remission (CR) + partial remission (PR) + stable disease (SD) lasting >6 months) and toxicity of the combination in triple negative metastatic breast cancer patients who have had 0-3 prior chemotherapy regimens. This design has > 80% power to test the null hypothesis i.e. clinical benefit rate is ≤ 10% vs. alternative hypothesis that clinical benefit rate is ≥ 30%. Prior carboplatin is allowed. Women with treated brain metastasis are eligible. Originally, carboplatin AUC 6 was to be administered every 3 weeks along with daily 5mg of RAD001 with a 3 patient run-in and then 10 mg daily. Due to a surprising amount of thrombocytopenia, the dose of carboplatin was first amended to AUC 5 and most recently to AUC 4 with 5 mg of RAD001 (no escalation to 10 mg). Results: 23 out of 25 patients have been recruited. Median age is 59. Thus far, there have been 1 CR, 5 PR’s, 8 SD's and 6 PD’s. One SD was achieved in a patient progressing on single agent carboplatin at study entry. Median duration of response is 13 weeks (range: 6-74 weeks). 5 patients had grade 3/4 thrombocytopenia and 4 patients had grade 3 neutropenia (no febrile neutropenia). 13 patients had treatment held and/or dose reductions secondary to hematological toxicity. Since dosing amendment for carboplatin to AUC 4 the regimen has been well tolerated (only 1 patient with grade 3 neutropenia and thrombocytopenia). 1 patient had grade 3 dehydration. The estimated clinical benefit rate is 45% (95% C.I.: 23%, 67%). Median time to progression or death is 85 days from start of treatment. Conclusions: Our study has met the primary end point of demonstrating clinical benefit in triple-negative metastatic breast cancer. Dose-limiting thrombocytopenia was an unexpected side effect requiring protocol amendment. Patient accrual continues at the amended dosing.