P1-17-07: Phase II Trial of RAD001 Plus Carboplatin in Patients with Triple-Negative Metastatic Breast Cancer.
Authors: Singh JC , Stein S , Volm M , Smith J , Novik Y , Speyer J , Adams S , Meyers M , Muggia F , Schneider R , Formenti S , Omene C , Choi H , Davis S , Goldberg J , Tiersten A 
Published: June 2012

Background: RAD001 is an oral mTOR inhibitor that has exhibited activity in breast cancer. Triple negative breast cancer cells are unable to repair double stranded DNA breaks and hence have sensitivity to platinum agents that cause interstrand cross-links. Rapamycin acts synergistically with platinum agents to induce apoptosis and inhibit proliferation in at least two different breast cancer cell lines (including ER/PR negative cell lines). We propose that combination RAD001 and carboplatin may have activity in triple-negative breast cancer.

Methods: The primary objective of the study is to determine clinical benefit (complete remission (CR) + partial remission (PR) + stable disease (SD)) and the toxicity of this combination in women with triple negative metastatic breast cancer who have had 0–3 prior chemotherapy regimens for metastatic disease. Secondary objectives are to determine progression free survival as well as investigating the relationship between pretreatment sensitivity (biopsy at baseline) and clinical response (biopsy post 2 cycles) using IHC staining for abundance of key proteins in the Akt-mTOR pathway and their activity using surrogate phosphorylation site-specific antibodies (Akt and phospho-serine 473, phospho-threonine and phospho-threonine 308 Akt; mTOR and phospho-serine 2448 mTOR; ribosome protein S6 kinase (S6K) and phospho-threonine 378 S6K; 4E-BP1 and phospho-serine 65 4E-BP1). Prior carboplatin is allowed. Women with treated brain metastasis are eligible. According to the original study plan, carboplatin AUC 6, was to be given intravenously every three weeks. Five mg of RAD001 was to be given daily with a 3 patient run-in and then 10 mg daily if there were no dose-limiting toxicities. Due to a unexpected amount of thrombocytopenia with this combination the dose of carboplatin was first amended to AUC 5 and most recently to AUC 4 with 5 mg of RAD001 (and no plan to escalate to 10 mg).

Results: Fourteen patients of a planned 25 have been recruited thus far. Median age is 58.5. Median number of prior regimens is 2 (0-3). Of the 7 patients assessable for response at this time, there have been 2 PR's and 5 patients with SD. One SD was achieved in a patient progressing on single agent carboplatin at study entry. Median duration of SD + PR is 28.5 weeks (5 patients have ongoing response ranging from 8–46.5 weeks). Five of 8 patients assessable for toxicity had grade 3 or 4 thrombocytopenia and 2 patients had grade 3 neutropenia. No cases of febrile neutropenia were observed. Four patients have required blood transfusion and one patient has required platelet transfusion. All patients have had treatment held and/or dose reductions secondary to hematological toxicity, however, since amended carboplatin dose the regimen has been very well tolerated with only one out of six patients) with grade 3 neutropenia and grade 3 thrombocytopenia. There have been no non-hematological grade 3 or 4 toxicities.

Conclusions: Clinical benefit was observed in all 7 assessable patients. Dose limiting thrombocytopenia was an unexpected side effect requiring protocol amendment. We continue to accrue study subjects at the amended dosing.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-17-07.