Paclitaxel pharmacokinetics and response to chemotherapy in patients with advanced cancer treated with a weekly regimen.

BACKGROUND: Paclitaxel pharmacokinetics were shown to be related to toxicity and survival. PATIENTS AND METHODS: We evaluated the effects of time above paclitaxel concentrations of 0.05 micromol/l (T(>0.05) and systemic exposures (AUC) to total and unbound paclitaxel (tPAC, uPAC) on response in patients with advanced cancer treated with weekly 1-h or 3-h infusions. RESULTS: After 6 weeks of therapy (WOT), 13 out of 21 assessable patients showed either partial response (PR) or stable disease (SD), while 8 had progressive disease (PD). As compared to patients with PD, those with PR or SD showed similar AUCs to uPAC and tPAC but higher (p < 0.05) T (>0.05). Patients with T(>0.05) > or = 20.7 hours had lower probability (p < 0.05) to progress within 12 WOT. CONCLUSION: Taking the heterogeneity of the studied tumor types into account, we found T(>0.05) to be associated with response to treatment. This emphasizes the value of threshold models for the investigation of paclitaxel pharmacodynamics.