Phase 2 Study With Pharmacokinetics (Pk) Analysis Of Sorafenib And Vinorelbine In Metastatic Breast Cancer

Background Sorafenib (S) is an oral inhibitor of the Raf, VEGFR and PDGFR pathways that contribute to chemoresistance in cancer cells. The combination of S with chemotherapy agents (capecitabine, paclitaxel) in metastatic breast cancer (BC) resulted in improved progression-free survival. In preclinical models of BC, favorable effects were noted combining S and vinorelbine (V). S and V are both metabolized through hepatic isoenzymes CYP3A, with the potential of PK interactions. A previous phase 1b study documented the feasibility of this combination. We aimed to define the activity and safety of this regimen in advanced BC and to investigate PK interactions of the 2 drugs at full doses. Methods Eligible patients were affected by Her2 negative, chemotherapy-naive metastatic BC, with measurable (RECIST) disease, adequate renal, liver and bone marrow functions and LVEF Δ50%. Treatment included V (30 mg/m 2 days 1, 8 every 21) + S (400 mg bid continuously), with dose reductions for grade 2-4 toxicities. Patients still benefiting after 8 cycles of treatment could continue on single-agent S. Six patients underwent PK analysis, starting treatment with S on day 4 of the first cycle, allowing for comparison of PK of each agent (V and S) administered alone versus during concomitant treatment with the other agent. Results 27 evaluable patients started on treatment, median age 57 (35-78); they received a median of 8 cycles to date (1-28), with 4 patients still on treatment. 44% of patients required at least one dose reduction for toxicity. One patient died of complicated sepsis after febrile neutropenia. Other significant toxicities included: febrile neutropenia (8%), uncomplicated Grade 3 (G3)-G4 neutropenia (60%); G3 fatigue (20%), hand-foot syndrome (12%), diarrhea (4%), enteritis (4%), hypertension (4%), asymptomatic increase of AST/ALT (16%), amylase (12%), lipase (8%), GGT (4%); G2 decrease in LVEF (4%), rash (16%), alopecia (20%). 33% of patients had a partial response, 85% experienced a clinical benefit (including stable disease after at least 4 cycles of treatment). Median progression-free survival was 5.5 months (95% CI 4.6-7.5). PK analysis showed no statistically significant interaction between S and N. Also the conversion of S to its metabolite S-N-oxide was not affected by the concomitant treatment with V. A non-significant trend was noticed for higher Cmax/AUC of V in the first 30 minutes after infusion when administered with ongoing treatment with S. Conclusions Combining S with V is feasible, but not devoid of toxicity, for which frequent dose reductions are necessary. A PK interaction could not be ruled out with the small sample size analyzed. More frail patients should start at a lower dose of both agents and we recommend close monitoring for the first 2 cycles, including amylase and lipase. Promising efficacy of this combination was observed, with a very high rate of disease control. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2706. doi:1538-7445.AM2012-2706