The pharmacokinetics and pharmacodynamics of high-dose paclitaxel monotherapy (825 mg/m² continuous infusion over 24 h) with hematopoietic support in women with metastatic breast cancer

Abstract

Purpose: We evaluated the pharmacokinetics and pharmacodynamics of high-dose paclitaxel (HDP) monotherapy (825 mg/m² continuous infusion over 24 h) with peripheral blood progenitor cell (PBPC) and G-CSF support in 17 women with metastatic breast cancer. Methods: Pharmacokinetic and pharmacodynamic data were collected in 17 women entered in a phase II trial of sequential HDP, and high-dose melphalan and cyclophosphamide/thiotepa/carboplatin. Results: The maximal plasma concentration (C_max), area under the plasma concentration time curve (AUC), apparent clearance (Cl_app), duration of plasma concentration above 0.05 µM (t>0.05 µM) for paclitaxel were (means±SD): 9.11±7.45 µM, 145±88 µM·h, 8.06±2.90 l/h per m² and 82.4±31.2 h, respectively. There was a significant correlation between the plasma paclitaxel concentration at 1 h (r ²=0.87), 12 h (r ²=0.85)and 23 h (r ²=0.92)and the AUC (P<0.0001). Duration of neutropenia was brief (median 3 days, range 0–5 days) and neutrophil recovery occurred earlier (median 6 days, range 0–7 days) than could be attributed to infused PBPC. Median nadir count for platelets was 66×10⁹/l (range 13–160×10⁹/l). Pharmacodynamic analysis showed no correlation between pharmacokinetic parameters (C_max, AUC, t>0.05 µM) and time to neutropenic nadir, duration of neutropenia, platelet count nadir and grades of neuropathy or mucositis. In ten patients in whom detailed neurologic and nerve conduction studies were performed, linear regression analysis showed a significant correlation between pre- and post-HDP treatment total neuropathy scores (r ²=0.46, P=0.03). Conclusions: HDP (825 mg/m² continuous infusion over 24 h) did not appear to be myeloablative. The degree of neurotoxicity subsequent to HDP was associated with the degree of baseline neuropathy but was not predictable from pharmacokinetic parameters.